Chemistry

Chemistry

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Contents Articles Overview

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Alchemy

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Chemistry

19

History of chemistry

33

Alchemy and chemistry in medieval Islam

43

Timeline of chemistry

47

Atoms and molecules

65

Atom

65

Atomic nucleus

86

Proton

92

Neutron

98

Electron

108

Chemical element

131

Isotope

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Ion

158

Molecule

164

Chemical compound

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Chemical substance

170

Common phases of matter

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Phases

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Gas

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Liquid

191

Solid

197

Periodic table

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Valence electron

209

Periodic table

212

Periodic trends

222

Period

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Group

229

Chemical concepts

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Ionic radius

231

Effective nuclear charge

240

Electronegativity

243

Mole

252

Lewis structure

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Chemical bond

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Chemical reactions

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Chemical reaction

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Chemical law

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Solution

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Acid

289

Reduction–oxidation

300

Miscellaneous

308

Etymology

308

Chemical industry

310

References Article Sources and Contributors

318

Image Sources, Licenses and Contributors

328

Article Licenses License

333

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Overview Alchemy Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base metals into the noble metals gold or silver, as well as an elixir of life conferring youth and immortality. In general alchemists believe in a natural and symbolic unity of humanity with the cosmos. Lately western alchemy has become recognized as the proto-typical protoscience presaging the seminal western sciences such as chemistry and medicine. Alchemists nurtured a framework of theory, terminology, experimental process and basic lab techniques still recognizable today. But alchemy differs from modern science in the inclusion of Hermetic principles and practices related to mythology, religion, and spirituality.

Overview

Page from alchemic treatise of Ramon Llull, 16th century

The best known goals of the alchemists were the transmutation of common metals into gold or silver, and the creation of a "panacea," a remedy that supposedly would cure all diseases and prolong life indefinitely; and the discovery of a universal solvent.[1] Modern discussions of alchemy are generally split into an examination of its exoteric practical applications, and its esoteric aspects. The former is pursued by historians of the physical sciences who have examined the subject in terms of proto-chemistry, medicine, and charlatanism. The latter is of interest to the historians of esotericism, psychologists, spiritual and new age communities, and hermetic philosophers.[2] The subject has also made an ongoing impact on literature and the arts. Despite the modern split, numerous sources stress an integration of esoteric and exoteric approaches to alchemy. Holmyard, when writing on exoteric aspects, states that they can not be properly appreciated if the esoteric is not always kept in mind.[3] The prototype for this model can be found in Bolos of Mendes' second century BCE work, Physika kai Mystika (On Physical and Mystical Matters).[4] Marie-Louise von Franz tells us the double approach of Western alchemy was set from the start, when Greek philosophy was mixed with Egyptian and Mesopotamian technology. The technological, operative approach, which she calls extraverted, and the mystic, contemplative, psychological one, which she calls introverted are not mutually exclusive, but complementary instead, as meditation requires practice in the real world, and conversely.[5]

Relation to the science of chemistry Practical applications of alchemy produced a wide range of contributions to medicine and the physical sciences. Alchemists Jābir ibn Hayyān[6] and Robert Boyle[7] are both credited as being the fathers of chemistry. Paracelsian iatrochemistry emphasized the medicinal application of alchemy (continued in plant alchemy, or spagyric).[8] Studies of alchemy also influenced Isaac Newton's theory of gravity.[9] Academic historical research supports that the alchemists were searching for a material substance using physical methods.[10]

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It is a popular belief that Alchemists made contributions to the "chemical" industries of the day—ore testing and refining, metalworking, production of gunpowder, ink, dyes, paints, cosmetics, leather tanning, ceramics, glass manufacture, preparation of extracts, liquors, and so on (it seems that the preparation of aqua vitae, the "water of life", was a fairly popular "experiment" among European alchemists). Alchemists contributed distillation to Western Europe. The attempts of alchemists to arrange information on substances, so as to clarify and anticipate the products of their chemical reactions, resulted in early conceptions of chemical elements and the first rudimentary periodic tables. They learned how to extract metals from ores, and how to compose many types of inorganic acids and bases. During the 17th century, practical alchemy started to evolve into modern chemistry,[11] as it was renamed by Robert Boyle, the "father of modern chemistry".[12] In his book, The Skeptical Chymist, Boyle attacked Paracelsus and the natural philosophy of Aristotle, which was taught at universities. However, Boyle's biographers, in their emphasis that he laid the foundations of modern chemistry, neglect how steadily he clung to the Scholastic sciences and to Alchemy, in theory, practice and doctrine.[13] The decline of alchemy continued in the 18th century with the birth of modern chemistry, which provided a more precise and reliable framework within a new view of the universe based on rational materialism.

Relation to Hermeticism In the eyes of a variety of esoteric and Hermetic practitioners, the heart of alchemy is spiritual. Transmutation of lead into gold is presented as an analogy for personal transmutation, purification, and perfection.[4] This approach is often termed 'spiritual', 'esoteric', or 'internal' alchemy. Early alchemists, such as Zosimos of Panopolis (c. 300 A.D.), highlight the spiritual nature of the alchemical quest, symbolic of a religious regeneration of the human soul.[14] This approach continued in the Middle Ages, as metaphysical aspects, substances, physical states, and material processes were used as metaphors for spiritual entities, spiritual states, and, ultimately, transformation. In this sense, the literal meanings of 'Alchemical Formulas' were a blind, hiding their true spiritual philosophy. Practitioners and patrons such as Melchior Cibinensis and Pope Innocent VIII existed within the ranks of the church, while Martin Luther applauded alchemy for its consistency with Christian teachings.[15] Both the transmutation of common metals into gold and the universal panacea symbolized evolution from an imperfect, diseased, corruptible, and ephemeral state towards a perfect, healthy, incorruptible, and everlasting state; and the philosopher's stone then represented a mystic key that would make this evolution possible. Applied to the alchemist himself, the twin goal symbolized his evolution from ignorance to enlightenment, and the stone represented a hidden spiritual truth or power that would lead to that goal. In texts that are written according to this view, the cryptic alchemical symbols, diagrams, and textual imagery of late alchemical works typically contain multiple layers of meanings, allegories, and references to other equally cryptic works; and must be laboriously decoded to discover their true meaning. In his 1766 Alchemical Catechism, Théodore Henri de Tschudi denotes that the usage of the metals was a symbol:

“

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Q. When the Philosophers speak of gold and silver, from which they extract their matter, are we to suppose that they refer to the vulgar gold [16] and silver? A. By no means; vulgar silver and gold are dead, while those of the Philosophers are full of life.

During the renaissance, alchemy broke into more distinct schools placing spiritual alchemists in high contrast with those working with literal metals and chemicals.[17] While most spiritual alchemists also incorporate elements of exotericism, examples of a purely spiritual alchemy can be traced back as far as the sixteenth century, when Jacob Boehme used alchemical terminology in strictly mystical writings.[18] Another example can be found in the work of Heinrich Khunrath (1560–1605) who viewed the process of transmutation as occurring within the alchemist's soul.[17] The recent work of Principe and Newman, seeks to reject the 'spiritual interpretation' of alchemy, stating it arose as a product of the Victorian occult revival.[19] There is evidence to support that some classical alchemical sources were

Alchemy adulterated during this time to give greater weight to the spiritual aspects of alchemy.[20] [21] Despite this, other scholars such as Calian and Tilton reject this view as entirely historically inaccurate, drawing examples of historical spiritual alchemy from Boehme, Isaac Newton, and Michael Maier.[22]

Etymology The word alchemy derives from the Old French alquimie, which is from the Medieval Latin alchimia, and which is in turn from the Arabic al-kimia (‫)ﺍﻟﻜﻴﻤﻴﺎء‬. This term itself is derived from the Ancient Greek chemeia (χημεία) or chemia (χημία)[23] with the addition of the Arabic definite article al- (‫)ﺍﻟـ‬.[24] The ancient Greek word may have been derived from[25] a version of the Egyptian name for Egypt, which was itself based on the Ancient Egyptian word kēme (hieroglyphic Khmi, black earth, as opposed to desert sand).[24] The word could also have originally derived from chumeia (χυμεία) meaning "mixture" and referring to pharmaceutical chemistry.[26] With the later rise of alchemy in Alexandria, the word may have derived from Χημία, and thus became spelled as χημεία, and the original meaning forgotten.[27] The etymology is still open, and recent research indicates that the Egyptian derivation may be valid.[28]

History Alchemy covers several philosophical traditions spanning some four millennia and three continents. These traditions' general penchant for cryptic and symbolic language makes it hard to trace their mutual influences and "genetic" relationships. One can distinguish at least three major strands, which appear to be largely independent, at Extract and symbol key from a 17th century book on alchemy. The symbols used least in their earlier stages: Chinese have a one-to-one correspondence with symbols used in astrology at the time. alchemy, centered in China and its zone of cultural influence; Indian alchemy, centered around the Indian subcontinent; and Western alchemy, which occurred around the Mediterranean and whose center has shifted over the millennia from Greco-Roman Egypt, to the Islamic world, and finally medieval Europe. Chinese alchemy was closely connected to Taoism and Indian alchemy with the Dharmic faiths, whereas Western alchemy developed its own philosophical system that was largely independent of, but influenced by, various Western religions. It is still an open question whether these three strands share a common origin, or to what extent they influenced each other.

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Alchemy in Greco-Roman Egypt The origin of Western alchemy may generally be traced to Hellenistic Egypt. The Hellenistic city of Alexandria was a center of Greek alchemical knowledge, and retained its preeminence through most of the Greek and Roman periods.[29] Here, elements of technology, religion, mythology, and Greek philosophy, each with their own much longer histories, combined to form the earliest known records of alchemy in the West. Zosimos of Panopolis wrote the oldest known books on alchemy while Mary the Jewess is credited as being the first non-fictitious Western alchemist. They wrote in Greek and lived in Egypt under Roman rule. Ambix, cucurbit and retort of Zosimos, from Marcelin Berthelot, Collection des anciens alchimistes grecs (3 vol., Paris, 1887–1888).

Mythology – It is claimed by Zosimos of Panopolis that alchemy dated back to pharaonic Egypt where it was the domain of the priestly [30] class; there is little or no evidence for such a claim though. Alchemical writers used Classical figures from Greek, Roman, and Egyptian mythology to illuminate their works and allegorize alchemical transmutation.[31] These included the pantheon of gods related to the Classical planets, Isis, Osiris, Jason, and many others. The central figure in the mythology of alchemy is Hermes Trismegistus (or Thrice-Great Hermes). His name is derived from the god Thoth and his Greek counterpart Hermes. Hermes and his caduceus or serpent-staff, were among alchemy's principal symbols. According to Clement of Alexandria, he wrote what were called the "forty-two books of Hermes", covering all fields of knowledge.[32] The Hermetica of Thrice-Great Hermes is generally understood to form the basis for Western alchemical philosophy and practice, called the hermetic philosophy by its early practitioners. These writings were collected in the first centuries of the common era. Technology – The dawn of Western alchemy is sometimes associated with that of metallurgy, extending back to 3500 BCE.[33] Many writings were lost when the emperor Diocletian ordered the burning of alchemical books[34] after suppressing a revolt in Alexandria (292 CE). Few original Egyptian documents on alchemy have survived, most notable among them the Stockholm papyrus and the Leyden papyrus X. Dating from 300 to 500 CE, they contained recipes for dyeing and making artificial gemstones, cleaning and fabricating pearls, and the manufacture of imitation gold and silver.[35] These writings lack the mystical, philosophical elements of alchemy, but do contain the works of Bolus of Mendes (or Pseudo-Democritus) which aligned these recipes with theoretical knowledge of astrology and the Classical elements.[36] Between the time of Bolus and Zosimos, the change took place that transformed this metallurgy into a Hermetic art.[37] Philosophy – Alexandria acted as a melting pot for philosophies of Pythagoreanism, Platonism, Stoicism and Gnosticism which formed the origin of alchemy’s character.[38] An important example of alchemy’s roots in Greek philosophy, originated by Empedocles and developed by Aristotle, was that all things in the universe were formed from only four elements: earth, air, water, and fire. According to Aristotle, each element had a sphere to which it belonged and to which it would return if left undisturbed.[39] The four elements of the Greek were mostly qualitative aspects of matter, not quantitative, as our modern elements are. "...True alchemy never regarded earth, air, water, and fire as corporeal or chemical substances in the present-day sense of the word. The four elements are simply the primary, and most general, qualities by means of which the amorphous and purely quantitative substance of all

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bodies first reveals itself in differentiated form."[40] Later alchemists extensively developed the mystical aspects of this concept. Alchemy coexisted alongside emerging Christianity. Lactantius believed Hermes Trismegistus had prophesied its birth. Augustine (354–430 CE) later affirmed this, but also condemned Trismegistus for idolatry.[41] Examples of Pagan, Christian, and Jewish alchemists can be found during this period. Most of the Greco-Roman alchemists preceding Zosimos are known only by pseudonyms, such as Moses, Isis, Cleopatra, Democritus, and Ostanes. Others authors such as Komarios, and Chymes, we only know through fragments of text. After 400 CE, Greek alchemical writers occupied themselves solely in commenting on the works of these predecessors.[42] By the middle of the seventh century alchemy was almost an entirely mystical discipline.[43] It was at that time that Khalid Ibn Yazid sparked its migration from Alexandria to the Islamic world, facilitating the translation and preservation of Greek alchemical texts in the 8th and 9th centuries.[44]

Alchemy in the Islamic world After the fall of the Roman Empire, the focus of alchemical development moved to the Islamic World. Much more is known about Islamic alchemy because it was better documented: indeed, most of the earlier writings that have come down through the years were preserved as Arabic translations.[45] The word alchemy itself was derived from the Arabic word ‫ ﺍﻟﻜﻴﻤﻴﺎء‬al-kimia. The Islamic world was a melting pot for alchemy. Platonic and Aristotelian thought, which had already been somewhat appropriated into hermetical science, continued to be assimilated during the late 7th and early 8th centuries. In the late 8th century, Jabir ibn Hayyan (known as "Geber" in Europe) introduced a new approach to alchemy, based on scientific methodology and controlled experimentation in the laboratory, in contrast to the ancient Greek and Egyptian alchemists whose works were often allegorical and unintelligible, with very little concern for laboratory work.[46] Jabir is thus "considered by many to be the father of chemistry",[47] albeit others reserve that title for Robert Boyle or Antoine Lavoisier. The historian of science, Paul Kraus, wrote:[46]

Jabir ibn Hayyan (Geber), considered a "father of chemistry", introduced a scientific and experimental approach to alchemy.

“To form an idea of the historical place of Jabir’s alchemy and to tackle the problem of its sources, it is advisable to compare it with what remains to us of the alchemical literature in the Greek language. One knows in which miserable state this literature reached us. Collected by Byzantine scientists from the tenth century, the corpus of the Greek alchemists is a cluster of incoherent fragments, going back to all the times since the third century until the end of the Middle Ages.” “The efforts of Berthelot and Ruelle to put a little order in this mass of literature led only to poor results, and the later researchers, among them in particular Mrs. Hammer-Jensen, Tannery, Lagercrantz , von Lippmann, Reitzenstein, Ruska, Bidez, Festugiere and others, could make clear only few points of detail… The study of the Greek alchemists is not very encouraging. An even surface examination of the Greek texts shows that a very small part only was organized according to true experiments of laboratory: even the supposedly technical writings, in the state where we find them today, are unintelligible nonsense which refuses any interpretation. It is different with Jabir’s alchemy. The relatively clear description of the processes and the alchemical apparatuses, the methodical classification of the substances, mark an experimental spirit which is extremely far away from the weird and odd esotericism of the Greek texts. The theory on which Jabir supports his operations

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6 is one of clearness and of an impressive unity. More than with the other Arab authors, one notes with him a balance between theoretical teaching and practical teaching, between the `ilm and the `amal. In vain one would seek in the Greek texts a work as systematic as that which is presented for example in the Book of Seventy.”

Jabir himself clearly recognized and proclaimed the importance of experimentation as follows: The first essential in chemistry is that thou shouldest perform practical work and conduct experiments, for he who performs not practical work nor makes experiments will never attain to the least degree of mastery.[48] Early Islamic chemists such as Jabir Ibn Hayyan (‫ ﺟﺎﺑﺮ ﺑﻦ ﺣﻴﺎﻥ‬in Arabic, Geberus in Latin; usually rendered in English as Geber), Al-Kindi (Alkindus) and Muhammad ibn Zakarīya Rāzi (Rasis or Rhazes in Latin) contributed a number of key chemical discoveries, such as the muriatic (hydrochloric acid), sulfuric and nitric acids, and more. The discovery that aqua regia, a mixture of nitric and hydrochloric acids, could dissolve the noblest metal, gold, was to fuel the imagination of alchemists for the next millennium. Islamic philosophers also made great contributions to alchemical hermeticism. The most influential author in this regard was arguably Jabir. Jabir's ultimate goal was Takwin, the artificial creation of life in the alchemical laboratory, up to and including human life. He analyzed each Aristotelian element in terms of four basic qualities of hotness, coldness, dryness, and moistness.[49] According to Jabir, in each metal two of these qualities were interior and two were exterior. For example, lead was externally cold and dry, while gold was hot and moist. Thus, Jabir theorized, by rearranging the qualities of one metal, a different metal would result.[49] By this reasoning, the search for the philosopher's stone was introduced to Western alchemy. Jabir developed an elaborate numerology whereby the root letters of a substance's name in Arabic, when treated with various transformations, held correspondences to the element's physical properties. The elemental system used in medieval alchemy also originated with Jabir. His original system consisted of seven elements, which included the five classical elements (aether, air, earth, fire and water), in addition to two chemical elements representing the metals: sulphur, ‘the stone which burns’, which characterized the principle of combustibility, and mercury, which contained the idealized principle of metallic properties. Shortly thereafter, this evolved into eight elements, with the Arabic concept of the three metallic principles: sulphur giving flammability or combustion, mercury giving volatility and stability, and salt giving solidity.[50] The atomic theory of corpuscularianism, where all physical bodies possess an inner and outer layer of minute particles or corpuscles, also has its origins in the work of Jabir.[51] During the 9th to 14th centuries, alchemical theories faced criticism from a variety of practical Muslim chemists, including Ja'far al-Sadiq,[52] Alkindus,[53] Abū al-Rayhān al-Bīrūnī,[54] Avicenna[55] and Ibn Khaldun. In particular, they wrote refutations against the idea of the transmutation of metals.

Alchemy

Alchemy in Medieval Europe The introduction of alchemy to Latin Europe occurred on February 11th, 1144, with the completion of Robert of Chester’s translation of the Arabic Book of the Composition of Alchemy. Although European craftsmen and technicians preexisted, Robert notes in his preface that alchemy was unknown in Latin Europe at the time of his writing. The translation of Arabic texts concerning numerous disciplines including alchemy flourished in twelfth century Toledo, Spain, through contributors like Gerard of Cremona and Adelard of Bath.[56] Translations of the time included the Turba Philosophorum, and the works of Avicenna and al-Razi. These brought with them many new words to the European vocabulary for which there was no previous Latin equivalent. Alcohol, carboy, elixir, and athanor are examples.[57] Meanwhile, theologian contemporaries of the translators made strides towards the reconciliation of faith and experimental rationalism, thereby priming Europe for the influx of alchemical thought. Saint Painting by Joseph Wright of Derby, 1771 Anselm (1033–1109) put forth the opinion that faith and rationalism were compatible and encouraged rationalism in a Christian context. Peter Abelard followed Anselm's work, laying the foundation for acceptance of Aristotelian thought before the first works of Aristotle reached the West. Later, Robert Grosseteste (1170–1253) took Abelard's methods of analysis and added the use of observations, experimentation, and conclusions in making scientific evaluations. Grosseteste also did much work to bridge Platonic and Aristotelian thinking.[58] Through much of the twelfth and thirteenth centuries, alchemical knowledge in Europe remained centered around translations, and new Latin contributions were not made. The efforts of the translators were succeeded by that of the encyclopaedists. Albertus Magnus and Roger Bacon are the most notable of these.[59] Their works explained and summarized the newly imported alchemical knowledge in Aristotelian terms. There is little to suggest that Albertus Magnus (1193–1280), a Dominican, was himself an alchemist. In his authentic works such as the Book of Minerals, he observed and commented on the operations and theories of alchemical authorities like Hermes and Democritus, and unnamed alchemists of his time. Albertus critically compared these to the writings of Aristotle and Avicenna, where they concerned the transmutation of metals. From the time shortly after his death through to the fifteenth century, twenty-eight or more alchemical tracts were misattributed to him, a common practice giving rise to his reputation as an accomplished alchemist.[60] Likewise, alchemical texts have been attributed to Albert’s student Thomas Aquinas (1225–1274). Roger Bacon (1214–1294) was an Oxford Franciscan who studied a wide variety of topics including optics, languages and medicine. After studying the Pseudo-Aristotelian Secretum Secretorum around 1247, he dramatically shifted his studies towards a vision of a universal science which included alchemy and astrology. Bacon maintained that Albertus Magnus’ ignorance of the fundamentals of alchemy prevented a complete picture of wisdom. While alchemy was not more important to him than any of the other sciences, and he did not produce symbolic allegorical works, Bacon's contributions advanced alchemy’s connections to soteriology and Christian theology. Bacon’s writings demonstrated an integration of morality, salvation, alchemy, and the prolongation of life. His

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Alchemy correspondence with Pope Clement IV highlighted this integration, calling attention to the importance of alchemy to the papacy.[61] Like the Greeks before him, Bacon acknowledged the division of alchemy into the practical and theoretical. He notes that the theoretical lied outside the scope of Aristotle, the natural philosophers, and all Latin writers of his time. The practical however, confirmed the theoretical through experiment, and Bacon advocated its uses in natural science and medicine.[62] Soon after Bacon, the influential work of Pseudo-Geber (sometimes identified as Paul of Taranto) appeared. His Summa Perfectionis remained a staple summary of alchemical practice and theory through the medieval and renaissance periods. It was notable for its inclusion of practical chemical operations alongside sulphur-mercury theory, and the unusual clarity with which they were described.[63] By the end of the 13th century, alchemy had developed into a fairly structured system of belief. Adepts believed in the macrocosm-microcosm theories of Hermes, that is to say, they believed that processes that affect minerals and other substances could have an effect on the human body (for example, if one could learn the secret of purifying gold, one could use the technique to purify the human soul). They believed in the four elements and the four qualities as described above, and they had a strong tradition of cloaking their written ideas in a labyrinth of coded jargon set with traps to mislead the uninitiated. Finally, the alchemists practiced their art: they actively experimented with chemicals and made observations and theories about how the universe operated. Their entire philosophy revolved around their belief that man's soul was divided within himself after the fall of Adam. By purifying the two parts of man's soul, man could be reunited with God.[64] In the 14th century, alchemy became more accessible to Europeans outside the confines of Latin speaking churchmen and scholars. Alchemical discourse shifted from scholarly philosophical debate to an exposed social commentary on the alchemists themselves.[65] Dante, Piers the Ploughman, and Chaucer all painted unflattering pictures of alchemists as thieves and liars. Pope John XXII’s 1317 edict, Spondent quas non exhibent forbade the false promises of transmutation made by pseudo-alchemists.[66] In 1403, Henry IV of England banned the practice of multiplying metals. These critiques and regulations centered more around pseudo-alchemical charlatanism than the actual study of alchemy, which continued with an increasingly Christian tone. The 14th century saw the Christian imagery of death and resurrection employed in the alchemical texts of Petrus Bonus, John of Rupescissa and in works written in the name of Raymond Lull and Arnold of Villanova.[67] Nicolas Flamel lived from 1330 to 1417 and would serve as the archetype for the next phase of alchemy. He was not a religious scholar as were many of his predecessors, and his entire interest in the subject revolved around the pursuit of the philosopher's stone. His work spends a great deal of time describing the processes and reactions, but never actually gives the formula for carrying out the transmutations. Most of his work was aimed at gathering alchemical knowledge that had existed before him, especially as regarded the philosopher's stone.[68] Though the historical Flamel existed, the writings and legends assigned to him only appeared in 1612. Current scholarship suggests that they are fiction—another example of the tradition of pseudepigraphy and allegory in alchemical writing.[69] Through the late Middle Ages (1300–1500) alchemists were much like Flamel: they concentrated on looking for the philosophers' stone. Bernard Trevisan and George Ripley made similar contributions in the 14th and 15th centuries . Their cryptic allusions and symbolism led to wide variations in interpretation of the art.

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Alchemy in the Renaissance and modern age Further information: Renaissance magic and natural magic European alchemy continued in this way through the dawning of the Renaissance. The era also saw a flourishing of con artists who would use chemical tricks and sleight of hand to "demonstrate" the transmutation of common metals into gold, or claim to possess secret knowledge that—with a "small" initial investment—would surely lead to that goal. However, it is important to emphasize that the terms "chemia" and "alchemia" were used as synonyms in the Renaissance, and the differences between alchemy, chemistry and small-scale assaying and metallurgy were not as neat as in the present day. There were important overlaps between practitioners, and trying to classify them into wizards (alchemists), scientists (chemists) and craftsmen (metallurgists) is anachronistic. One of these men who emerged at the beginning of the 16th century was the German Heinrich Cornelius Agrippa (1486–1535). This alchemist believed himself to be a wizard capable of summoning spirits. His influence was negligible, but like Flamel, he produced writings which were referred to by alchemists of later years. Again like Flamel, he did much to change alchemy from a mystical philosophy to an occultist magic. He did keep alive the philosophies of the earlier alchemists, including experimental science, numerology, etc., but he added magic theory, which reinforced the idea of alchemy as an occultist belief. In spite of all this, Agrippa still considered himself a Christian, though his views often came into conflict with the church.[70] [71] The most important name in this period is Philippus Aureolus Paracelsus, (Theophrastus Bombastus von Hohenheim, 1493–1541) who cast alchemy into a new form, rejecting some of the occultism that had accumulated over the years and promoting the use of observations and experiments to learn about the human body. He rejected Gnostic traditions, but kept much of the Hermetical, neo-Platonic, and Pythagorean philosophies; however, Hermetical science had so much Aristotelian theory that his rejection of Gnosticism was practically meaningless. In particular, Paracelsus rejected the magic theories of Agrippa and Flamel. Paracelsus pioneered the use of chemicals and minerals in medicine, and wrote "Many have said of Alchemy, that it is for the making of gold and silver. For me such is not the aim, but to consider only what virtue and power may lie in medicines."[72] His hermetical views were that sickness and health in the body relied on the harmony of man the microcosm and Nature the macrocosm. He took an approach different from those before him, using this analogy not in the manner of soul-purification but in the manner that humans must have certain balances of minerals in their bodies, and that certain illnesses of the body had chemical remedies that could cure them.[73] While his attempts of treating diseases with such remedies as Mercury might seem ill-advised from a modern point of view, his basic idea of chemically produced medicines has stood time surprisingly well. Alchemy became known as the spagyric art after Greek words meaning to separate and to join together the word probably being coined by Paracelsus. Compare this with one of the dictums of Alchemy in Latin: Solve et Coagula  — Separate, and Join Together (or "dissolve and coagulate").[74]

"Alchemist Sędziwój" (1566–1636) by Jan Matejko, 1867

At the beginning of the 16th century, King James IV of Scotland kept an alchemist, John Damian, and a furnace of the quintessence in Stirling Castle.[75] In England, the topic of alchemy in that time frame is often associated with Doctor John Dee (13 July 1527 – December, 1608), better known for his role as astrologer, cryptographer, and general "scientific consultant" to Queen Elizabeth I. Dee was considered an authority on the works of Roger Bacon, and was interested enough in alchemy to write a book on that

Alchemy subject (Monas Hieroglyphica, 1564) influenced by the Kabbalah. Dee's associate Edward Kelley — who claimed to converse with angels through a crystal ball and to own a powder that would turn mercury into gold — may have been the source of the popular image of the alchemist-charlatan. Rudolf II, Holy Roman Emperor, in the late 16th century, sponsored various alchemists in their work at his court in Prague, one of which was a particular alchemist named Edward Kelley. Kelley had been a protegee of John Dee in England. Another lesser known alchemist was Michael Sendivogius (Michał Sędziwój, 1566–1636), a Polish alchemist, philosopher, medical doctor and pioneer of chemistry. According to some accounts, he distilled oxygen in a lab sometime around 1600, 170 years before Scheele and Priestley, by warming nitre (saltpetre). He thought of the gas given off as "the elixir of life". Shortly after discovering this method, it is believed that Sendivogious taught his technique to Cornelius Drebbel. In 1621, Drebbel practically applied this in a submarine. Tycho Brahe (1546–1601), better known for his astronomical and astrological investigations, was also an alchemist. He had a laboratory built for that purpose at his Uraniborg observatory/research institute. Up to the 17th century, alchemy was practiced by scientists, such as Isaac Newton – who devoted considerably more of his writing to the study of alchemy (see Isaac Newton's occult studies) than he did to either optics or physics. Other alchemists of the Western world who were eminent in their other studies include Roger Bacon, and Tycho Brahe.

The decline of Western alchemy The demise of Western alchemy was brought about by the rise of modern science with its emphasis on rigorous quantitative experimentation and its disdain for "ancient wisdom". Although the seeds of these events were planted as early as the 17th century, alchemy still flourished for some two hundred years, and in fact may have reached its apogee in the 18th century. As late as 1781 James Price claimed to have produced a powder that could transmute mercury into silver or gold. Robert Boyle (1627–1691), better known for his studies of gases (cf. Boyle's law) pioneered the scientific method in chemical investigations. He assumed nothing in his experiments and compiled every piece of relevant data; in a typical experiment, Boyle would note the place in which the experiment was carried out, the wind characteristics, the position of the Sun and Moon, and the barometer reading, all just in case they proved to be relevant.[76] This approach eventually led to the founding of modern chemistry in the 18th and 19th centuries, based on revolutionary discoveries of Lavoisier and John Dalton — which finally provided a logical, quantitative and reliable framework for understanding matter transmutations, and revealed the futility of longstanding alchemical goals such as the philosopher's stone. Meanwhile, Paracelsian alchemy led to the development of modern medicine. Experimentalists gradually uncovered the workings of the human body, such as blood circulation (Harvey, 1616), and eventually traced many diseases to infections with germs (Koch and Pasteur, 19th century) or lack of natural nutrients and vitamins (Lind, Eijkman, Funk, et al.). Supported by parallel developments in organic chemistry, the new science easily displaced alchemy from its medical roles, interpretive and prescriptive, while deflating its hopes of miraculous elixirs and exposing the ineffectiveness or even toxicity of its remedies. During the seventeenth century, a short-lived "supernatural" interpretation of alchemy become popular, including support by fellows of the Royal Society: Robert Boyle and Elias Ashmole. Proponents of the supernatural interpretation of alchemy believed that the philosopher's stone might be used to summon and communicate with angels.[77] In the 17th century, practical alchemy started to evolve into modern chemistry,[11] as it was renamed by Robert Boyle, the "father of modern chemistry".[12] In his book, The Skeptical Chymist, Boyle attacked Paracelsus and the venerable natural philosophy of Aristotle, which was taught at universities. However, Boyle's biographers, in their

10

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11

emphasis that he laid the foundations of modern chemistry, neglect how steadily he clung to the Scholastic sciences and to Alchemy, in theory, practice and doctrine.[13] The decline of alchemy continued in the 18th century with the birth of modern chemistry, which provided a more precise and reliable framework within a new view of the universe based on rational materialism. The words "alchemy" and "chemistry" were used interchangeably during most of the seventeenth century; only during the eighteenth century was a distinction drawn rigidly between the two.[78] In the eighteen century, "alchemy" was considered to be restricted to the realm of "gold making", leading to the popular belief that most, if not all, alchemists were charlatans, and the tradition itself nothing more than a fraud.[79] The obscure and secretive writings of the alchemists was used as a case by those who wished to forward a fraudulent and non-scientific opinion of alchemy.[80] In order to protect the developing science of modern chemistry from the negative censure of which alchemy was being subjected, academic writers during the scientific Enlightenment attempted, for the sake of survival, to separate and divorce the "new" chemistry from the "old" practices of alchemy. This move was mostly successful, and the consequences of this continued into the nineteenth and twentieth centuries, and even to the present day.[81] During the occult revival of the early nineteenth century, alchemy received new attention as an occult science.[82] The esoteric or occultist school, which arose during the nineteenth century, held (and continues to hold) the view that the substances and operations mentioned in alchemical literature are to be interpreted in a spiritual sense, and it downplays the role of the alchemy as a practical tradition or protoscience.[83] This interpretation further forwarded the view that alchemy is an art primarily concerned with spiritual enlightenment or illumination, as opposed to the physical manipulation of apparatus and chemicals, and claims that the obscure language of the alchemical texts were an allegorical guise for spiritual, moral or mystical processes.[84] In the first half of the 19th century, one established chemist, Baron Carl Reichenbach, worked on concepts similar to the old alchemy, such as the Odic force, but his research did not enter the mainstream of scientific discussion. In the nineteenth century revival of alchemy, the two most seminal figures were Mary Anne Atwood, and Ethan Allen Hitchcock who independently published similar works regarding spiritual alchemy. Both forwarded a completely esoteric view of alchemy, as Atwood claimed: "No modern art or chemistry, notwithstanding all its surreptitious claims, has any thing in common with Alchemy." [85] [86] Atwood's work influenced subsequent authors of the occult revival including Eliphas Levi, Arthur Edward Waite, and Rudolf Steiner. Hitchcock, in his Remarks Upon Alchymists (1855) attempted to make a case for his spiritual interpretation with his claim that the alchemists wrote about a spiritual discipline under a materialistic guise in order to avoid accusations of blasphemy from the church and state. Thus, as science steadily continued to uncover and rationalize the clockwork of the universe, founded on its own materialistic metaphysics, alchemy was left deprived of its chemical and medical connections — but still incurably burdened by them. Reduced to an arcane philosophical system, poorly connected to the material world, it suffered the common fate of other esoteric disciplines such as astrology and Kabbalah: excluded from university curricula, shunned by its former patrons, ostracized by scientists, and commonly viewed as the epitome of charlatanism and superstition. These developments could be interpreted as part of a broader reaction in European intellectualism against the Romantic movement of the preceding centuries.

Indian alchemy According to Multhauf & Gilbert (2008):[87] The oldest Indian writings, the Vedas (Hindu sacred scriptures), contain the same hints of alchemy that are found in evidence from ancient China, namely vague references to a connection between gold and long life. Mercury, which was so vital to alchemy everywhere, is first mentioned in the 4th- to 3rd-century-BC Artha-śāstra, about the same time it is encountered in China and in the West. Evidence of the idea of transmuting base metals to gold appears in 2nd- to 5th-century-AD Buddhist texts, about

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12 the same time as in the West. Since Alexander the Great had invaded Ancient India in 325 BC, leaving a Greek state (Gandhāra) that long endured, the possibility exists that the Indians acquired the idea from the Greeks, but it could have been the other way around.

Significant progress in alchemy was made in ancient India. Will Durant wrote in Our Oriental Heritage: "Something has been said about the chemical excellence of cast iron in ancient India, and about the high industrial development of the Gupta times, when India was looked to, even by Imperial Rome, as the most skilled of the nations in such chemical industries as dyeing, tanning, soap-making, glass and cement... By the sixth century the Hindus were far ahead of Europe in industrial chemistry; they were masters of calcinations, distillation, sublimation, steaming, fixation, the production of light without heat, the mixing of anesthetic and soporific powders, and the preparation of metallic salts, compounds and alloys. The tempering of steel was brought in ancient India to a perfection unknown in Europe till our own times; King Porus is said to have selected, as a specially valuable gift from Alexander, not gold or silver, but thirty pounds of steel. The Moslems took much of this Hindu chemical science and industry to the Near East and Europe; the secret of manufacturing "Damascus" blades, for example, was taken by the Arabs from the Persians, and by the Persians from India." An 11th century Persian chemist and physician named Abū Rayhān Bīrūnī reported that they "have a science similar to alchemy which is quite peculiar to them, which in Sanskrit is called Rasayāna and in Persian Rasavātam. It means the art of obtaining/manipulating Rasa: nectar, mercury, and juice. This art was restricted to certain operations, metals, drugs, compounds, and medicines, many of which have mercury as their core element. Its principles restored the health of those who were ill beyond hope and gave back youth to fading old age." One thing is sure though, Indian alchemy like every other Indian science is focused on finding Moksha: perfection, immortality, liberation. As such it focuses its efforts on transmutation of the human body: from mortal to immortal. Many are the traditional stories of alchemists still alive since time immemorial due to the effects of their experiments. The texts of Ayurvedic Medicine and Science have aspects similar to alchemy: concepts of cures for all known diseases, and treatments that focus on anointing the body with oils. Since alchemy eventually became engrained in the vast field of Indian erudition, influences from other metaphysical and philosophical doctrines such as Samkhya, Yoga, Vaisheshika and Ayurveda were inevitable. Nonetheless, most of the Rasayāna texts track their origins back to Kaula tantric schools associated to the teachings of the personality of Matsyendranath. The Rasayāna was understood by very few people at the time. Two famous examples were Nagarjunacharya and Nityanadhiya. Nagarjunacharya was a Buddhist monk who, in ancient times, ran the great university of Nagarjuna Sagar. His famous book, Rasaratanakaram, is a famous example of early Indian medicine. In traditional Indian medicinal terminology "rasa" translates as "mercury" and Nagarjunacharya was said to have developed a method to convert the mercury into gold. Much of his original writings are lost to us, but his teachings still have strong influence on traditional Indian medicine (Ayurveda) to this day.

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Chinese alchemy Whereas Western alchemy eventually centered on the transmutation of base metals into noble ones, Chinese alchemy had a more obvious connection to medicine. The philosopher's stone of European alchemists can be compared to the Grand Elixir of Immortality sought by Chinese alchemists. However, in the hermetic view, these two goals were not unconnected, and the philosopher's stone was often equated with the universal panacea; therefore, the two traditions may have had more in common than initially appears. Taoist Alchemists often

Black powder may have been an important invention of Chinese alchemists. Described in use this alternate version 9th century texts and used in fireworks in China by the 10th century, it was used in of the Taijitu. cannons by 1290. From China, the use of gunpowder spread to Japan, the Mongols, the Arab world, and Europe. Gunpowder was used by the Mongols against the Hungarians in 1241, and in Europe by the 14th century. Chinese alchemy was closely connected to Taoist forms of traditional Chinese medicine, such as Acupuncture and Moxibustion, and to martial arts such as Tai Chi Chuan and Kung Fu (although some Tai Chi schools believe that their art derives from the philosophical or hygienic branches of Taoism, not Alchemical). In fact, in the early Song Dynasty, followers of this Taoist idea (chiefly the elite and upper class) would ingest mercuric sulfide, which, though tolerable in low levels, led many to suicide. Thinking that this consequential death would lead to freedom and access to the Taoist heavens, the ensuing deaths encouraged people to eschew this method of alchemy in favor of external sources (the aforementioned Tai Chi Chuan, mastering of the Qi, etc.).

Alchemy as a subject of historical research The history of alchemy has become a significant and recognized subject of academic study.[88] As the language of the alchemists is analyzed, historians are becoming more aware of the intellectual connections between that discipline and other facets of Western cultural history, such as the evolution of science and philosophy, the sociology and psychology of the intellectual communities, kabbalism, spiritualism, Rosicrucianism, and other mystic movements.[89] Institutions involved in this research include The Chymistry of Isaac Newton project at Indiana University, the University of Exeter Centre for the Study of Esotericism (EXESESO), the European Society for the Study of Western Esotericism (ESSWE), and the University of Amsterdam's Sub-department for the History of Hermetic Philosophy and Related Currents. A large collection of books on alchemy is kept in the Bibliotheca Philosophica Hermetica in Amsterdam.

Modern alchemy Due to the complexity and obscurity of alchemical literature, and the eighteenth century disappearance of remaining alchemical practitioners into the area of chemistry; the general understanding of alchemy in the general public, modern practitioners, and also many historians of science, have been strongly influenced by several distinct and radically different interpretations.[90] Hundreds of books including adulterated translations of classical alchemical literature were published throughout the early nineteenth century.[20] Many of these continue to be reprinted today by esoteric book publishing houses, along with modern books on spiritual alchemy and poor translations of older alchemical texts. These are then used as sources by modern authors to support spiritual interpretations. Over half of the books on alchemy published since 1970 support spiritual interpretations, mostly using previously adulterated documents to support their conclusions. Many of these books continue to be taken seriously, even appearing in university bookshelves.[91] Esoteric interpretations of alchemy remains strong to this day, and continue to influence both the public and academic perceptions of the history of alchemy. Today, numerous esoteric alchemical groups continue to perpetuate modern interpretations of alchemy, sometimes merging in concepts from New Age or radical environmentalism

Alchemy movements.[92] Rosencrutzians and freemasons have a continued interest in alchemy and its symbolism.

Alchemy in traditional medicine Traditional medicine sometimes involves the transmutation of natural substances, using pharmacological or a combination of pharmacological and spiritual techniques. In Ayurveda the samskaras are claimed to transform heavy metals and toxic herbs in a way that removes their toxicity. These processes are actively used to the present day.[93] Twentieth century spagyrists Albert Richard Riedel and Jean Dubuis merged Paracelsian alchemy with occultism, teaching laboratory pharmaceutical methods. The schools they founded, Les Philosophes de la Nature and The Paracelsus Research Society, popularized modern spagyrics including the manufacture of herbal tinctures and products.[94] The courses, books, organizations, and conferences generated by their students continue to influence popular applications of alchemy as a new age medicinal practice.

Nuclear transmutation In 1919, Ernest Rutherford used artificial disintegration to convert nitrogen into oxygen.[95] From then on, this sort of scientific transmutation is routinely performed in many nuclear physics-related laboratories and facilities, like particle accelerators, nuclear power stations and nuclear weapons as a by-product of fission and other physical processes. The synthesis of noble metals enjoyed brief popularity in the 20th century when physicists were able to convert platinum atoms into gold atoms via a nuclear reaction. However, the new gold atoms, being unstable isotopes, lasted for under five seconds before they broke apart. More recently, reports of table-top element transmutation—by means of electrolysis or sonic cavitation—were the pivot of the cold fusion controversy of 1989. None of those claims have yet been reliably duplicated. Synthesis of noble metals requires either a nuclear reactor or a particle accelerator. Particle accelerators use huge amounts of energy, while nuclear reactors produce energy, so only methods utilizing a nuclear reactor are of economic interest.

Psychology Alchemical symbolism has been used by psychologists such as Carl Jung who reexamined alchemical symbolism and theory and presented the inner meaning of alchemical work as a spiritual path.[96] [97] Jung was deeply interested in the occult since his youth, participating in seances, which he used as the basis for his doctoral dissertation "On the Psychology and Pathology of So-Called Occult Phenomena."[98] In 1913, Jung had already adopted a "spiritualist and redemptive interpretation of alchemy", likely reflecting his interest in the occult literature of the nineteenth century.[99] Jung began writing his views on alchemy from the 1920s and continued until the end of his life. His interpretation of Chinese alchemical texts in terms of his analytical psychology also served the function of comparing Eastern and Western alchemical imagery and core concepts and hence its possible inner sources (archetypes).[100] [101] [102] Jung saw alchemy as a Western proto-psychology dedicated to the achievement of individuation.[96] [102] In his interpretation, alchemy was the vessel by which Gnosticism survived its various purges into the Renaissance,[102] [103] a concept also followed by others such as Stephan A. Hoeller. In this sense, Jung viewed alchemy as comparable to a Yoga of the East, and more adequate to the Western mind than Eastern religions and philosophies. The practice of Alchemy seemed to change the mind and spirit of the Alchemist. Conversely, spontaneous changes on the mind of Western people undergoing any important stage in individuation seems to produce, on occasion, imagery known to Alchemy and relevant to the person's situation.[104] Jung did not completely reject the material experiments of the alchemists, but he massively downplayed it, writing that the transmutation was performed in the mind of the alchemist. He claimed the material substances and procedures were only a projection of the alchemists' internal state, while the real substance to be transformed was the mind itself.[105]

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Alchemy Marie-Louise von Franz, a disciple of Jung, continued Jung's studies on alchemy and its psychological meaning. Jung's work exercised a great influence on the mainstream perception of alchemy, his approach becoming a stock element in many popular texts on the subject to this day.[106] Modern scholars are sometimes critical of the Jungian approach to alchemy as overly reflective of nineteenth century occultism.[107]

Magnum opus The Great Work of Alchemy is often described as a series of four stages represented by colors. • • • •

nigredo, a blackening or melanosis albedo, a whitening or leucosis citrinitas, a yellowing or xanthosis rubedo, a reddening, purpling, or iosis[108]

Notes [1] Alchemy at Dictionary.com (http:/ / dictionary. reference. com/ browse/ alchemy). [2] For a detailed look into the problems of defining alchemy see Stanton J. Linden. Darke Hierogliphicks: Alchemy in English literature from Chaucer to the Restoration. University Press of Kentucky, 1996. pp. 6–36 [3] E. J. Holmyard. Alchemy. p.16 [4] Antoine Faivre, Wouter J. Hanegraaff. Western esotericism and the science of religion. 1995. p.96 [5] von Franz, M-L. Alchemical Active Imagination. Shambala. Boston. 1997. ISBN 0-87773-589-1. [6] N.C. Datta. The Story of Chemistry. p.23 [7] Arthur Greenburg. From alchemy to chemistry in picture and story. [8] H. Stanley Redgrove. Alchemy Ancient and Modern p.60 [9] Mitch Stokes. Isaac Newton p. 57 [10] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, pp 397–8,400 [11] William R Newman & Lawrence M Principe (1998) "The Etymological Origins of an Historiographic Mistake" in Early Science and Medicine, Vol. 3, No. 1 pp. 32–65 [12] Deem, Rich (2005). "The Religious Affiliation of Robert Boyle the father of modern chemistry. From: Famous Scientists Who Believed in God" (http:/ / www. adherents. com/ people/ pb/ Robert_Boyle. html). adherents.com. . Retrieved 2009-04-17. [13] More, Louis Trenchard (January 1941). "Boyle as Alchemist". Journal of the History of Ideas (University of Pennsylvania Press) 2 (1): 61–76. doi:10.2307/2707281. JSTOR 2707281. [14] Allen G. Debus. Alchemy and early modern chemistry. The Society for the History of Alchemy and Chemistry. p.34. [15] Raphael Patai. The Jewish Alchemists: A History and Source Book. Princeton University Press. p.4 [16] Théodore Henri de Tschudi. Hermetic Catechism in his L'Etoile Flamboyant ou la Société des Franc-Maçons considerée sous tous les aspects. 1766. (A.E. Waite translation as found in The Hermetic and Alchemical Writings of Paracelsus.) [17] Raphael Patai. The Jewish Alchemists: A History and Source Book. Princeton University Press. p.3 [18] Daniel Merkur. Gnosis: an esoteric tradition of mystical visions and unions. State University of New York Press. p.75 [19] Alchemy Tried in the Fire by William R. Newman, Lawrence M Principe, p37 [20] Newton and Newtonianism by James E. Force, Sarah Hutton, p211 [21] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, pp 395–6 [22] Calian, George (2010). Alkimia Operativa and Alkimia Speculativa. Some Modern Controversies on the Historiography of Alchemy. Annual of Medieval Studies at CEU. [23] alchemy (http:/ / oxforddictionaries. com/ view/ entry/ m_en_gb0017630#DWS-M_EN_GB-037342), Oxford Dictionaries [24] " alchemy (http:/ / oed. com/ search?searchType=dictionary& q=alchemy)". Oxford English Dictionary. Oxford University Press. 2nd ed. 1989. Or see Harper, Douglas. "alchemy" (http:/ / www. etymonline. com/ index. php?term=alchemy). Online Etymology Dictionary. . Retrieved 2010-04-07.. [25] See, for example, the etymology for χημεία in Liddell, Henry George; Robert Scott (1901). A Greek-English Lexicon (Eighth edition, revised throughout ed.). Oxford: Clarendon Press. ISBN 0199102058. [26] See, for example, both the etymology given in the Oxford English Dictionary and also that for χυμεία in Liddell, Henry George; Robert Scott, Henry Stuart Jones (1940). A Greek-English Lexicon (http:/ / www. perseus. tufts. edu/ hopper/ morph?l=xumeia& la=greek#lexicon) (A new edition, revised and augmented throughout ed.). Oxford: Clarendon Press. ISBN 0199102058. . [27] The original source for this analysis is the article on pp. 81–85 of Mahn, Carl August Friedrich (1855). Etymologische untersuchungen auf dem gebiete der romanischen sprachen (http:/ / books. google. com/ ?id=-BMLAAAAQAAJ). F. Duemmler. . [28] The article by David Bain, entitled "Μελανίτις γή, an unnoticed Greek name for Egypt: New evidence for the origins and etymology of alchemy?" expresses the current debate. The world of ancient magic (http:/ / www. norwinst. gr/ papers. html). Bergen: The Norwegian

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Alchemy Institute at Athens. 1999. . [29] New Scientist, December 24–31, 1987 [30] Garfinkel, Harold (1986). Ethnomethodological Studies of Work. Routledge &Kegan Paul. pp. 127. ISBN 0415119650. [31] Yves Bonnefoy. ‘Roman and European Mythologies’. University of Chicago Press, 1992. pp. 211–213 [32] Clement, Stromata, vi. 4. [33] Stanton J. Linden. Darke Hierogliphicks: Alchemy in English literature from Chaucer to the Restoration. University Press of Kentucky, 1996. p.12 [34] Partington, James Riddick (1989). A Short History of Chemistry. New York: Dover Publications. pp. 20. ISBN 0486659771. [35] The Alchemy Reader: From Hermes Trismegistus to Isaac Newton, Stanton J. Linden, Cambridge University Press, 2003, p46 [36] A History of Chemistry, Bensaude-Vincent, Isabelle Stengers, Harvard University Press, 1996, p13 [37] Stanton J. Linden. Darke Hierogliphicks: Alchemy in English literature from Chaucer to the Restoration. University Press of Kentucky, 1996. p.14 [38] A History of Chemistry, Bensaude-Vincent, Isabelle Stengers, Harvard University Press, 1996, p13 [39] Lindsay, Jack (1970). The Origins of Alchemy in Graeco-Roman Egypt. London: Muller. p. 16. ISBN 0-389-01006-5. [40] Hitchcock, Ethan Allen (1857). Remarks Upon Alchemy and the Alchemists. Boston: Crosby, Nichols. p. 66. ISBN 0405079559. [41] Fanning, Philip Ashley. Isaac Newton and the Transmutation of Alchemy: An Alternative View of the Scientific Revolution. 2009. p.6 [42] F. Sherwood Taylor. Alchemists, Founders of Modern Chemistry. p.26. [43] Allen G. Debus. Alchemy and early modern chemistry: papers from Ambix. p. 36 [44] Glen Warren Bowersock, Peter Robert Lamont Brown, Oleg Grabar. Late antiquity: a guide to the postclassical world. p. 284–285 [45] Burckhardt, Titus (1967). Alchemy: Science of the Cosmos, Science of the Soul. Trans. William Stoddart. Baltimore: Penguin. p. 46. ISBN 0906540968. [46] Kraus, Paul, Jâbir ibn Hayyân, Contribution à l'histoire des idées scientifiques dans l'Islam. I. Le corpus des écrits jâbiriens. II. Jâbir et la science grecque,. Cairo (1942–1943). Repr. By Fuat Sezgin, (Natural Sciences in Islam. 67–68), Frankfurt. 2002: (cf. Ahmad Y Hassan. "A Critical Reassessment of the Geber Problem: Part Three" (http:/ / www. history-science-technology. com/ Geber/ Geber 3. htm). . Retrieved 2008-08-09.) [47] Derewenda, Zygmunt S. (2007). "On wine, chirality and crystallography". Acta Crystallographica Section A: Foundations of Crystallography 64: 246–258 [247]. doi:10.1107/S0108767307054293. PMID 18156689. [48] Holmyard, E. J. (1931). Makers of Chemistry (http:/ / www. archive. org/ details/ makersofchemistr029725mbp). Oxford: Clarendon Press. p. 60. . [49] Burckhardt, Titus (1967). Alchemy: Science of the Cosmos, Science of the Soul. Trans. William Stoddart. Baltimore: Penguin. p. 29. ISBN 0906540968. [50] Strathern, Paul. (2000), Mendeleyev’s Dream – the Quest for the Elements, New York: Berkley Books [51] Moran, Bruce T. (2005). Distilling knowledge: alchemy, chemistry, and the scientific revolution. Harvard University Press. p. 146. ISBN 0674014952. "a corpuscularian tradition in alchemy stemming from the speculations of the medieval author Geber (Jabir ibn Hayyan)" [52] Research Committee of Strasburg University, Imam Jafar Ibn Muhammad As-Sadiq A.S. The Great Muslim Scientist and Philosopher, translated by Kaukab Ali Mirza, 2000. Willowdale Ont. ISBN 0969949014. [53] Felix Klein-Frank (2001), "Al-Kindi", in Oliver Leaman & Hossein Nasr, History of Islamic Philosophy, p. 174. London: Routledge. [54] Marmura Michael E. (1965). "An Introduction to Islamic Cosmological Doctrines: Conceptions of Nature and Methods Used for Its Study by the Ikhwan Al-Safa'an, Al-Biruni, and Ibn Sina by Seyyed Hossein Nasr". Speculum 40 (4): 744–6. doi:10.2307/2851429. [55] Robert Briffault (1938). The Making of Humanity, p. 196–197. [56] E.J. Holmyard. Alchemy. 1990. p.105-108 [57] E.J. Holmyard. Alchemy. 1990. p.110 [58] Hollister, C. Warren (1990). Medieval Europe: A Short History (6th ed.). Blacklick, Ohio: McGraw–Hill College. pp. 294f. ISBN 0-07-557141-2. [59] John Read. From Alchemy to Chemistry. 1995 p.90 [60] James A. Weisheipl. Albertus Magnus and the Sciences: Commemorative Essays. PIMS. 1980. p.187-202 [61] Edmund Brehm. "Roger Bacon’s Place in the History of Alchemy." Ambix. Vol. 23, Part I, March 1976. [62] E.J. Holmyard. Alchemy. Courier Dover Publications, 1990. p.120-121 [63] E.J. Holmyard Alchemy. Dover. 1990. p. 134-141. [64] Burckhardt, Titus (1967). Alchemy: Science of the Cosmos, Science of the Soul. Trans. William Stoddart. Baltimore: Penguin. p. 149. ISBN 0906540968. [65] Tara E. Nummedal. Alchemy and Authority in the Holy Roman Empire. University of Chicago Press, 2007. p. 49 [66] John Hines, II, R. F. Yeager. John Gower, Trilingual Poet: Language, Translation, and Tradition. Boydell & Brewer. 2010. p.170 [67] Leah DeVun. From Prophecy, Alchemy, and the End of Time: John of Rupescissa in the late middle ages. Columbia University Press, 2009. p. 104 [68] Burckhardt, Titus (1967). Alchemy: Science of the Cosmos, Science of the Soul. Trans. William Stoddart. Baltimore: Penguin. pp. 170–181. ISBN 0906540968. [69] Stanton J. Linden. The Alchemy Reader: From Hermes Trismegistus to Isaac Newton. Cambridge University Press, 2003. p.123 [70] Edwardes, Michael (1977). The Dark Side of History. New York: Stein and Day. pp. 56–59. ISBN 0552114634.

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[71] Wilson, Colin (1971). The Occult: A History. New York: Random House. pp. 23–29. ISBN 0-394-46555-5. [72] Edwardes, Michael (1977). The Dark Side of History. New York: Stein and Day. p. 47. ISBN 0552114634. [73] Debus, Allen G. and Multhauf, Robert P. (1966). Alchemy and Chemistry in the Seventeenth Century. Los Angeles: William Andrews Clark Memorial Library, University of California.. pp. 6–12. [74] Davis, Erik. "The Gods of the Funny Books: An Interview with Neil Gaiman and Rachel Pollack" (http:/ / www. techgnosis. com/ gaiman. html). Gnosis (magazine). Techgnosis (reprint from Summer 1994 issue). . Retrieved 2007-02-04. [75] Accounts of the Lord High Treasurer of Scotland, vol. iii, (1901), 99, 202, 206, 209, 330, 340, 341, 353, 355, 365, 379, 382, 389, 409. [76] Pilkington, Roger (1959). Robert Boyle: Father of Chemistry. London: John Murray. p. 11. • • •

Journal of the History of Ideas, 41, 1980, p293-318 Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p399 The Aspiring Adept: Robert Boyle and His Alchemical Quest, by Lawrence M. Principe, 'Princeton University Press', 1998, pp 188 90

• Alchemy Tried in the Fire by William R. Newman, Lawrence M Principe, p37 • Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p386 [79] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p386 [80] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p387 [81] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, pp 386–7 • •

On the Edge of the Future by Jeffrey John Kripal, Glenn W. Shuck, p27 Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p387

• • •

Alchemy Tried in the Fire by William R. Newman, Lawrence M Principe, p37 The Theosophical Enlightenment by Mircea Eliade, State University of New York Press, 1994, p49 Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p388

[84] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p388 [85] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p391 [86] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p143. [87] Multhauf, Robert P. & Gilbert, Robert Andrew (2008). Alchemy. Encyclopædia Britannica (2008). [88] Antoine Faivre, Wouter J. Hanegraaff. Western esotericism and the science of religion. 1995. p.viii–xvi [89] See Exeter Centre for the Study of Esotericism website (http:/ / centres. exeter. ac. uk/ exeseso/ ) [90] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p385 [91] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, pp 395–6 [92] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p396 [93] Junius, Manfred M; The Practical Handbook of Plant Alchemy: An Herbalist's Guide to Preparing Medicinal Essences, Tinctures, and Elixirs; Healing Arts Press 1985 [94] Joscelyn Godwin. The Golden Thread: The Ageless Wisdom of the Western Mystery Traditions. Quest Books, 2007. p.120 [95] [ |Amsco School Publications (http:/ / worthyisthelamb. info/ amsco/ newtitles. html)]. "Reviewing Physics: The Physical Setting" (http:/ / www. stmary. ws/ physics/ amsco_review_and_glencoe/ chapter05. pdf). Amsco School Publications. . ""The first artificial transmutation of one element to another was performed by Rutherford in 1919. Rutherford bombarded nitrogen with energetic alpha particles that were moving fast enough to overcome the electric repulsion between themselves and the target nuclei. The alpha particles collided with, and were absorbed by, the nitrogen nuclei, and protons were ejected. In the process oxygen and hydrogen nuclei were created." [96] Jung, C. G. (1944). Psychology and Alchemy (2nd ed. 1968 Collected Works Vol. 12 ISBN 0-691-01831-6). London: Routledge. [97] Jung, C. G., & Hinkle, B. M. (1912). Psychology of the Unconscious : a study of the transformations and symbolisms of the libido, a contribution to the history of the evolution of thought. London: Kegan Paul Trench Trubner. (revised in 1952 as Symbols of Transformation, Collected Works Vol.5 ISBN 0-691-01815-4). [98] The Jung Cult, by Ricard Noll, Princeton University Press, 1994, p144 [99] Noll. Aryan Christ. p171 [100] C.-G. Jung Preface to Richard Wilhelm's translation of the I Ching. [101] C.-G. Jung Preface to the translation of The Secret of The Golden Flower. [102] Polly Young-Eisendrath, Terence Dawson. The Cambridge companion to Jung. Cambridge University Press. 1997. p.33 [103] Jung, C. G., & Jaffe A. (1962). Memories, Dreams, Reflections. London: Collins. This is Jung's autobiography, recorded and edited by Aniela Jaffe, ISBN 0-679-72395-1. [104] Jung, C. G.—Psychology and Alchemy; Symbols of Transformation. [105] Redemption in Alchemy, by Carl Jung, p210 [106] Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p401 • • •

Secrets of Nature, Astrology and Alchemy in Modern Europe by William R. Newman, Anthony Grafton, MIT Press, 2006, p418 Alchemy Tried in the Fire, by William R. Newman, Lawrence M. Principe, p37 On the Edge of the Future, by Jeffrey John Kripal, Glenn W. Shuck, p27

[108] Joseph Needham. Science & Civilisation in China: Chemistry and chemical technology. Spagyrical discovery and invention : magisteries of gold and immortality. Cambridge. 1974. p.23

Alchemy

References • Calian, George (2010). Alkimia Operativa and Alkimia Speculativa. Some Modern Controversies on the Historiography of Alchemy (http://www.archive.org/stream/AlkimiaOperativaAndAlkimiaSpeculativa. SomeModernControversiesOnThe/FlorinGeorgeCalian-AlkimiaOperativaAndAlkimiaSpeculativa. SomeModernControversiesOnTheHistoriographyOfAlchemy#page/n0/mode/2up). Annual of Medieval Studies at CEU. • Eliade, Mircea (1978). The Forge and the Crucible (http://books.google.com/books?id=SQDJ1aCtMV8C& printsec=frontcover#v=onepage&q&f=false). Chicago: University of Chicago Press. • Halleux, Robert (1979). Les textes alchimiques. Brepols Publishers. • Holmyard, Eric John (1957). Alchemy (http://books.google.com/books?id=7Bt-kwKRUzUC&lpg=PP1& dq=alchemy&pg=PP1&hl=en#v=onepage&q&f=false). Courier Dover Publications. • Janacek, Bruce, Alchemical Belief: Occultism in the Religious Culture of Early Modern England (University Park (PA), Pennsylvania State UP, 2011) (Magic in History). • Linden, Stanton J. (2003). The Alchemy Reader: from Hermes Trismegistus to Isaac Newton (http://books. google.com/books?id=isJY9jWdru0C&lpg=PP1&dq=alchemy&pg=PP1#v=onepage&q&f=false). Cambridge University Press. • Newman, William R.; Principe, Lawrence M. (2002). Alchemy Tried in the Fire (http://books.google.com/ books?id=eQERmMdykZEC&lpg=PP1&dq=alchemy&pg=PP1#v=onepage&q&f=false). The University of Chicago Press.. • von Franz, Marie Louise (1980). Alchemy: An Introduction to the Symbolism and the Psychology (http://books. google.com/books?id=wOVUUMirSnEC&lpg=PP1&dq=alchemy&pg=PP1#v=onepage&q&f=false). Inner City Books.

External links • Alchemy (http://www.bbc.co.uk/programmes/p003k9bn) on In Our Time at the BBC. ( listen now (http:// www.bbc.co.uk/iplayer/console/p003k9bn/In_Our_Time_Alchemy)) • Etymology of "alchemy" (http://www.balashon.com/2009/03/alchemy.html) • Hidden Symbolism of Alchemy and the Occult Arts (http://www.gutenberg.org/etext/27755) Full-length book by Herbert Silberer • Alchemy images (http://www.alchemywebsite.com/emb_apparatus.html) • Dictionary of the History of Ideas: (http://xtf.lib.virginia.edu/xtf/view?docId=DicHist/uvaBook/tei/ DicHist1.xml;chunk.id=dv1-04) Alchemy • Antiquity, Vol. 77 (2003) "A 16th century lab in a 21st century lab". (http://antiquity.ac.uk/ProjGall/martinon/ index.html) —Origins of modern chemistry in alchemy • The Story of Alchemy and the Beginnings of Chemistry (http://www.gutenberg.org/etext/14218), Muir, M. M. Pattison (1913) • "Transforming the Alchemists" (http://www.nytimes.com/2006/08/01/science/01alch. html?ex=1312084800&en=4445e5f8f9c7b3c0&ei=5090&partner=rssuserland&emc=rss), New York Times, August 1, 2006. Recent historical scholarship on alchemy. • Electronic library (http://www.revistaazogue.com/biblio.htm#N_3_) with hundreds of alchemical books (15th and 20th century) and 160 original manuscripts. • SHAC: Society for the History of Alchemy and Chemistry (http://www.ambix.org/) • Book of Secrets: Alchemy and the European Imagination, 1500-2000 (http://beinecke.library.yale.edu/ digitallibrary/alchemy.html) A digital exhibition from the Beinecke Rare Book and Manuscript Library at Yale University (http://www.library.yale.edu/beinecke/)

18

Chemistry

19

Chemistry Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties.[1] [2] Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds. Chemistry is sometimes called "the central science" because it connects physics with other natural sciences such as geology and biology.[3] [4] Chemistry is a branch of physical science but distinct from physics.[5] The etymology of the word chemistry has been much disputed.[6] The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East.[7]

Chemistry is the science of atomic matter (that made of chemical elements), its properties, structure, composition and its changes during interactions and chemical reactions.

Theory Traditional chemistry starts with the study of elementary particles, atoms, molecules,[8] substances, metals, crystals and other aggregates of matter. in solid, liquid, and gas states, whether in isolation or combination. The interactions, reactions and transformations that are studied in chemistry are a result of interaction either between different chemical substances or between matter and energy. Such behaviors are studied in a chemistry laboratory using various forms of laboratory glassware. During chemical reactions, bonds between atoms break and form, resulting in different substances with different properties. In a blast furnace, iron oxide, a compound, reacts with carbon monoxide to form iron, one of the chemical elements, and carbon dioxide.

A chemical reaction is a transformation of some substances into one or more other substances.[9] It can be symbolically depicted through a chemical equation. The number of atoms on the left and the right in the equation for a chemical transformation is most often equal. The nature of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of Laboratory, Institute of Biochemistry, University their structure, phase as well as their chemical compositions. They can of Cologne be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists.[10] Most chemists specialize in one or more sub-disciplines.

Chemistry

20

History Ancient Egyptians pioneered the art of synthetic "wet" chemistry up to 4,000 years ago.[11] By 1000 BC ancient civilizations were using technologies that formed the basis of the various branches of chemistry such as; extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze. The genesis of chemistry can be traced to the widely observed phenomenon of burning that led to metallurgy—the art and science of processing ores to get metals (e.g. metallurgy in ancient India). The greed for gold led to the discovery of the process for its purification, even though the underlying principles were not well understood—it was thought to be a transformation rather than purification. Many scholars in those days thought it reasonable to believe that there exist means for transforming cheaper (base) metals into gold. This gave way to alchemy and the search for the Philosopher's Stone which was believed to bring about such a transformation by mere touch.[12] Greek atomism dates back to 440 BC, as what might be indicated by the book De Rerum Natura (The Nature of Things)[13] written by the Roman Lucretius in 50 BC.[14] Much of the early development of purification methods is described by Pliny the Elder in his Naturalis Historia.

Democritus' atomist philosophy was later adopted by Epicurus (341–270 BCE).

A tentative outline is as follows: 1. Egyptian alchemy [3,000 BCE – 400 BCE], formulate early "element" theories such as the Ogdoad. 2. Greek alchemy [332 BCE – 642 CE], the Macedonian king Alexander the Great conquers Egypt and founds Alexandria, having the world's largest library, where scholars and wise men gather to study. 3. Islamic alchemy [642 CE – 1200], the Muslim conquest of Egypt; development of alchemy by Jābir ibn Hayyān, al-Razi and others; Jābir modifies Aristotle's theories; advances in processes and apparatus.[15] 4. European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry. From the 12th century, major advances in the chemical arts shifted from Arab lands to western Europe.[15] 5. Chemistry [1661], Boyle writes his classic chemistry text The Sceptical Chymist. 6. Chemistry [1787], Lavoisier writes his classic Elements of Chemistry. 7. Chemistry [1803], Dalton publishes his Atomic Theory. 8. Chemistry [1869], Dmitri Mendeleev presented his Periodic table being the framework of the modern chemistry The earliest pioneers of Chemistry, and inventors of the modern scientific method,[16] were medieval Arab and Persian scholars. They introduced precise observation and controlled experimentation into the field and discovered numerous Chemical substances.[17] "Chemistry as a science was almost created by the Muslims; for in this field, where the Greeks (so far as we know) were confined to industrial experience and vague hypothesis, the Saracens introduced precise observation, controlled experiment, and careful records. They invented and named the alembic (al-anbiq), chemically analyzed innumerable substances, composed lapidaries, distinguished alkalis and acids, investigated their affinities, studied and manufactured hundreds of drugs. Alchemy, which the Muslims inherited from Egypt, contributed to chemistry by a thousand incidental discoveries, and by its method, which was the most scientific of all medieval operations." [17]

The most influential Muslim chemists were Jābir ibn Hayyān (Geber, d. 815), al-Kindi (d. 873), al-Razi (d. 925), al-Biruni (d. 1048) and Alhazen (d. 1039).[18] The works of Jābir became more widely known in Europe through Latin translations by a pseudo-Geber in 14th century Spain, who also wrote some of his own books under the pen

Chemistry name "Geber". The contribution of Indian alchemists and metallurgists in the development of chemistry was also quite significant.[19] The emergence of chemistry in Europe was primarily due to the recurrent incidence of the plague and blights there during the so called Dark Ages. This gave rise to a need for medicines. It was thought that there exists a universal medicine called the Elixir of Life that can cure all diseases, but like the Philosopher's Stone, it was never found. For some practitioners, alchemy was an intellectual pursuit, over time, they got better at it. Paracelsus (1493–1541), for example, rejected the 4-elemental theory and with only a vague understanding of his chemicals and medicines, formed a hybrid of alchemy and science in what was to be called iatrochemistry. Similarly, the influences of philosophers such as Sir Francis Bacon (1561–1626) and René Descartes (1596–1650), who demanded more rigor in mathematics and in removing bias from scientific observations, led to a scientific revolution. In chemistry, this began with Robert Boyle (1627–1691), who came up with an equation known as Boyle's Law about the characteristics of gaseous state.[21] Chemistry indeed came of age when Antoine Lavoisier (1743–1794), developed the theory of Conservation of mass in 1783; and the development of the Atomic Theory by John Dalton around 1800. The Law of Conservation of Mass resulted in the reformulation of chemistry based on this law and the oxygen theory of combustion, Antoine-Laurent de Lavoisier is considered the which was largely based on the work of Lavoisier. Lavoisier's [20] "Father of Modern Chemistry". fundamental contributions to chemistry were a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of the chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature and made contribution to the modern metric system. Lavoisier also worked to translate the archaic and technical language of chemistry into something that could be easily understood by the largely uneducated masses, leading to an increased public interest in chemistry. All these advances in chemistry led to what is usually called the chemical revolution. The contributions of Lavoisier led to what is now called modern chemistry—the chemistry that is studied in educational institutions all over the world. It is because of these and other contributions that Antoine Lavoisier is often celebrated as the "Father of Modern Chemistry".[22] The later discovery of Friedrich Wöhler that many natural substances, organic compounds, can indeed be synthesized in a chemistry laboratory also helped the modern chemistry to mature from its infancy.[23] The discovery of the chemical elements has a long history from the days of alchemy and culminating in the discovery of the periodic table of the chemical elements by Dmitri Mendeleev (1834–1907)[24] and later discoveries of some synthetic elements.

Etymology The word chemistry comes from the word alchemy, an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine; it is commonly thought of as the quest to turn lead or another common starting material into gold.[25] The word alchemy in turn is derived from the Arabic word al-kīmīā (‫)ﺍﻟﻜﻴﻤﻴﺎء‬, meaning alchemy. The Arabic term is borrowed from the Greek χημία or χημεία.[26] [27] This may have Egyptian origins. Many believe that al-kīmīā is derived from χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian.[26] Alternately, al-kīmīā may be derived from χημεία, meaning "cast together".[28]

21

Chemistry An alchemist was called a 'chemist' in popular speech, and later the suffix "-ry" was added to this to describe the art of the chemist as "chemistry".

Definitions In retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. Shown below are some of the standard definitions used by various noted chemists: • Alchemy (330) – the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos).[29] • Chymistry (1661) – the subject of the material principles of mixed bodies (Boyle).[30] • Chymistry (1663) – a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection (Glaser).[31] • Chemistry (1730) – the art of resolving mixed, compound, or aggregate bodies into their principles; and of composing such bodies from those principles (Stahl).[32] • Chemistry (1837) – the science concerned with the laws and effects of molecular forces (Dumas).[33] • Chemistry (1947) – the science of substances: their structure, their properties, and the reactions that change them into other substances (Pauling).[34] • Chemistry (1998) – the study of matter and the changes it undergoes (Chang).[35]

Basic concepts Several concepts are essential for the study of chemistry; some of them are:[36]

Atom An atom is the basic unit of chemistry. It consists of a positively charged core (the atomic nucleus) which contains protons and neutrons, and which maintains a number of electrons to balance the positive charge in the nucleus. The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

Element The concept of chemical element is related to that of chemical substance. A chemical element is specifically a substance which is composed of a single type of atom. A chemical element is characterized by a particular number of protons in the nuclei of its atoms. This number is known as the atomic number of the element. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, and all atoms with 92 protons in their nuclei are atoms of the element uranium. Although all the nuclei of all atoms belonging to one element will have the same number of protons, they may not necessarily have the same number of neutrons; such atoms are termed isotopes. In fact several isotopes of an element may exist. Ninety–four different chemical elements or types of atoms based on the number of protons are observed on earth naturally, having at least one isotope that is stable or has a very long half-life. A further 18 elements have been recognised by IUPAC after they have been made in the laboratory. The standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number and groups them by electron configuration. Due to its arrangement, groups, or columns, and periods, or rows, of elements in the table either share several chemical properties, or follow a certain trend in characteristics such as atomic radius, electronegativity, etc. Lists of the elements by name, by symbol, and by atomic number are also available.

22

Chemistry

Compound A compound is a substance with a particular ratio of atoms of particular chemical elements which determines its composition, and a particular organization which determines chemical properties. For example, water is a compound containing hydrogen and oxygen in the ratio of two to one, with the oxygen atom between the two hydrogen atoms, and an angle of 104.5° between them. Compounds are formed and interconverted by chemical reactions.

Substance A chemical substance is a kind of matter with a definite composition and set of properties.[37] Strictly speaking, a mixture of compounds, elements or compounds and elements is not a chemical substance, but it may be called a chemical. Most of the substances we encounter in our daily life are some kind of mixture; for example: air, alloys, biomass, etc. Nomenclature of substances is a critical part of the language of chemistry. Generally it refers to a system for naming chemical compounds. Earlier in the history of chemistry substances were given name by their discoverer, which often led to some confusion and difficulty. However, today the IUPAC system of chemical nomenclature allows chemists to specify by name specific compounds amongst the vast variety of possible chemicals. The standard nomenclature of chemical substances is set by the International Union of Pure and Applied Chemistry (IUPAC). There are well-defined systems in place for naming chemical species. Organic compounds are named according to the organic nomenclature system.[38] Inorganic compounds are named according to the inorganic nomenclature system.[39] In addition the Chemical Abstracts Service has devised a method to index chemical substance. In this scheme each chemical substance is identifiable by a number known as CAS registry number.

Molecule A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrograph. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry.

23

Chemistry

The "inert" or noble chemical elements (helium, neon, argon, krypton, xenon and radon) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. Identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. However, not all substances or chemical compounds consist of discrete molecules, and A molecular structure depicts the bonds and relative positions of atoms in a molecule indeed most of the solid substances such as that in Paclitaxel shown here that makes up the solid crust, mantle, and core of the Earth are chemical compounds without molecules. These other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. Instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. Examples of such substances are mineral salts (such as table salt), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. One of the main characteristic of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

Mole and amount of substance Mole is a unit to measure amount of substance (also called chemical amount). A mole is the amount of a substance that contains as many elementary entities (atoms, molecules or ions) as there are atoms in 0.012 kilogram (or 12 grams) of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state.[40] The number of entities per mole is known as the Avogadro constant, and is determined empirically. The currently accepted value is 6.02214179(30)×1023 mol−1 (2007 CODATA). One way to understand the meaning of the term "mole" is to compare and contrast it to terms such as dozen. Just as one dozen eggs contains 12 individual eggs, one mole contains 6.02214179(30)×1023 atoms, molecules or other particles. The term is used because it is much easier to say, for example, 1 mole of carbon, than it is to say 6.02214179(30)×1023 carbon atoms, and because moles of chemicals represent a scale that is easy to experience. The amount of substance of a solute per volume of solution is known as amount of substance concentration, or molarity for short. Molarity is the quantity most commonly used to express the concentration of a solution in the chemical laboratory. The most commonly used units for molarity are mol/L (the official SI units are mol/m3).

24

Chemistry

Ions and salts An ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. Positively charged cations (e.g. sodium cation Na+) and negatively charged anions (e.g. chloride Cl−) can form a crystalline lattice of neutral salts (e.g. sodium chloride NaCl). Examples of polyatomic ions that do not split up during acid-base reactions are hydroxide (OH−) and phosphate (PO43−). Ions in the gaseous phase are often known as plasma.

Acidity and basicity A substance can often be classified as an acid or a base. There are several different theories which explain acid-base behavior. The simplest is Arrhenius theory, which states than an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. According to Brønsted–Lowry acid-base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction; by extension, a base is the substance which receives that hydrogen ion. A third common theory is Lewis acid-base theory, which is based on the formation of new chemical bonds. Lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. According to concept as per Lewis, the crucial things being exchanged are charges.[41] There are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept [42] Acid strength is commonly measured by two methods. One measurement, based on the Arrhenius definition of acidity, is pH, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. Thus, solutions that have a low pH have a high hydronium ion concentration, and can be said to be more acidic. The other measurement, based on the Brønsted–Lowry definition, is the acid dissociation constant (Ka), which measure the relative ability of a substance to act as an acid under the Brønsted–Lowry definition of an acid. That is, substances with a higher Ka are more likely to donate hydrogen ions in chemical reactions than those with lower Ka values.

Phase In addition to the specific chemical properties that distinguish different chemical classifications chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications; however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. Sometimes the distinction between phases can be continuous instead of having a discrete boundary, in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution (that is, in water). Less familiar phases include plasmas, Bose-Einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. While most familiar phases deal with three-dimensional systems, it is also possible to define analogs in two-dimensional systems, which has received attention for its relevance to systems in biology.

25

Chemistry

Redox It is a concept related to the ability of atoms of various substances to lose or gain electrons. Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. An oxidant removes electrons from another substance. Similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. A reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number.

Bonding Atoms sticking together in molecules or crystals are said to be bonded with one another. A chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them.[43] More than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. A chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of Van der Waals force. Each of these kind of Electron atomic and molecular orbitals bond is ascribed to some potential. These potentials create the interactions which hold atoms together in molecules or crystals. In many simple compounds, Valence Bond Theory, the Valence Shell Electron Pair Repulsion model (VSEPR), and the concept of oxidation number can be used to explain molecular structure and composition. Similarly, theories from classical physics can be used to predict many ionic structures. With more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. See diagram on electronic orbitals.

Reaction When a chemical substance is transformed as a result of its interaction with another or energy, a chemical reaction is said to have occurred. Chemical reaction is therefore a concept related to the 'reaction' of a substance when it comes in close contact with another, whether as a mixture or a solution; exposure to some form of energy, or both. It results in some energy exchange between the constituents of the reaction as well with the system environment which may be a designed vessels which are often laboratory glassware. Chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more smaller molecules, or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction, dissociation, acid-base neutralization and molecular rearrangement are some of the commonly used kinds of chemical reactions. A chemical reaction can be symbolically depicted through a chemical equation. While in a non-nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons.[44] The sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. A chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. Many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. Reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical

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Chemistry reactions. Several empirical rules, like the Woodward-Hoffmann rules often come handy while proposing a mechanism for a chemical reaction. According to the IUPAC gold book a chemical reaction is a process that results in the interconversion of chemical species".[45] Accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. An additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. Such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (i.e. 'microscopic chemical events').

Equilibrium Although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible. For example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. A system of chemical substances at equilibrium even though having an unchanging composition is most often not static; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. Thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. Chemicals present in biological systems are invariably not at equilibrium; rather they are far from equilibrium.

Energy In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light; thus the products of a reaction may have more or less energy than the reactants. A reaction is said to be exergonic if the final state is lower on the energy scale than the initial state; in the case of endergonic reactions the situation is the reverse. A reaction is said to be exothermic if the reaction releases heat to the surroundings; in the case of endothermic reactions, the reaction absorbs heat from the surroundings. Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. The speed of a chemical reaction (at given temperature T) is related to the activation energy E, by the Boltzmann's population factor - that is the probability of molecule to have energy greater than or equal to E at the given temperature T. This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation. The activation energy necessary for a chemical reaction can be in the form of heat, light, electricity or mechanical force in the form of ultrasound.[46] A related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. A reaction is feasible only if the total change in the Gibbs free energy is negative, ; if it is equal to zero the chemical reaction is said to be at equilibrium. There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive; that is, more amenable to chemical reactions. The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H2O); a liquid at room temperature because its molecules are bound by hydrogen bonds.[47] Whereas hydrogen sulfide (H2S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole-dipole interactions.

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The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. Thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. For example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. The existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. Different kinds of spectra are often used in chemical spectroscopy, e.g. IR, microwave, NMR, ESR, etc. Spectroscopy is also used to identify the composition of remote objects - like stars and distant galaxies - by analyzing their radiation spectra.

Emission spectrum of iron

The term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances.

Chemical laws Chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. Some of them are: • • • • • • • • • • •

Avogadro's law Beer-Lambert law Boyle's law (1662, relating pressure and volume) Charles's law (1787, relating volume and temperature) Fick's law of diffusion Gay-Lussac's law (1809, relating pressure and temperature) Le Chatelier's Principle Henry's law Hess's Law Law of conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics. Law of conservation of mass continues to be conserved in isolated systems, even in modern physics. However, special relativity shows that due to mass-energy equivalence, whenever non-material "energy" (heat, light, kinetic energy) is removed from a non-isolated system, some mass will be lost with it. High energy loses result in loss of weighable amounts of mass, an important topic in nuclear chemistry. • Law of definite composition, although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. • Law of multiple proportions • Raoult's Law

Chemistry

Subdisciplines Chemistry is typically divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry.[48] • Analytical chemistry is the analysis of material samples to gain an understanding of their chemical composition and structure. Analytical chemistry incorporates standardized experimental methods in chemistry. These methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry. • Biochemistry is the study of the chemicals, chemical reactions and chemical interactions that take place in living organisms. Biochemistry and organic chemistry are closely related, as in medicinal chemistry or neurochemistry. Biochemistry is also associated with molecular biology and genetics. • Inorganic chemistry is the study of the properties and reactions of inorganic compounds. The distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub-discipline of organometallic chemistry. • Materials chemistry is the preparation, characterization, and understanding of substances with a useful function. The field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry with a focus on fundamental issues that are unique to materials. Primary systems of study include the chemistry of condensed phases (solids, liquids, polymers) and interfaces between different phases. • Neurochemistry is the study of neurochemicals; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. • Nuclear chemistry is the study of how subatomic particles come together and make nuclei. Modern Transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. • Organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. An organic compound is defined as any compound based on a carbon skeleton. • Physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. In particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. Important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry.[49] Physical chemistry has large overlap with molecular physics. Physical chemistry involves the use of infinitesimal calculus in deriving equations. It is usually associated with quantum chemistry and theoretical chemistry. Physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. • Theoretical chemistry is the study of chemistry via fundamental theoretical reasoning (usually within mathematics or physics). In particular the application of quantum mechanics to chemistry is called quantum chemistry. Since the end of the Second World War, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. Theoretical chemistry has large overlap with (theoretical and experimental) condensed matter physics and molecular physics. Other disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic (carbon based) matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the study of chemical processes using physical concepts such as thermodynamics and quantum mechanics; and analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines). Other fields include agrochemistry, astrochemistry (and cosmochemistry), atmospheric chemistry, chemical engineering, chemical biology, chemo-informatics, electrochemistry, environmental chemistry, femtochemistry,

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Chemistry flavor chemistry, flow chemistry, geochemistry, green chemistry, histochemistry, history of chemistry, hydrogenation chemistry, immunochemistry, marine chemistry, materials science, mathematical chemistry, mechanochemistry, medicinal chemistry, molecular biology, molecular mechanics, nanotechnology, natural product chemistry, oenology, organometallic chemistry, petrochemistry, pharmacology, photochemistry, physical organic chemistry, phytochemistry, polymer chemistry, radiochemistry, solid-state chemistry, sonochemistry, supramolecular chemistry, surface chemistry, synthetic chemistry, thermochemistry, and many others.

Chemical industry The chemical industry represents an important economic activity. The global top 50 chemical producers in 2004 had sales of 587 billion US dollars with a profit margin of 8.1% and research and development spending of 2.1% of total chemical sales.[50]

Professional societies • American Chemical Society • American Society for Neurochemistry • Chemical Institute of Canada • • • • • • • •

Chemical Society of Peru International Union of Pure and Applied Chemistry Royal Australian Chemical Institute Royal Netherlands Chemical Society Royal Society of Chemistry Society of Chemical Industry World Association of Theoretical and Computational Chemists List of chemistry societies

References [1] "What is Chemistry?" (http:/ / chemweb. ucc. ie/ what_is_chemistry. htm). Chemweb.ucc.ie. . Retrieved 2011-06-12. [2] Chemistry (http:/ / dictionary. reference. com/ browse/ Chemistry). (n.d.). Merriam-Webster's Medical Dictionary. Retrieved August 19, 2007. [3] Theodore L. Brown, H. Eugene Lemay, Bruce Edward Bursten, H. Lemay. Chemistry: The Central Science. Prentice Hall; 8 edition (1999). ISBN 0-13-010310-1. Pages 3-4. [4] Chemistry is seen as occupying an intermediate position in a hierarchy of the sciences by "reductive level" between physics and biology. See Carsten Reinhardt. Chemical Sciences in the 20th Century: Bridging Boundaries. Wiley-VCH, 2001. ISBN 3-527-30271-9. Pages 1-2. [5] Is chemistry a branch of physics? a paper by Mario Bunge (http:/ / www. springerlink. com/ content/ k97523j471763374/ ) [6] See: Chemistry (etymology) for possible origins of this word. [7] http:/ / etext. lib. virginia. edu/ cgi-local/ DHI/ dhi. cgi?id=dv1-04 [8] Matter: Atoms from Democritus to Dalton (http:/ / www. visionlearning. com/ library/ module_viewer. php?mid=49) by Anthony Carpi, Ph.D. [9] IUPAC Gold Book Definition (http:/ / www. iupac. org/ goldbook/ C01033. pdf) [10] "California Occupational Guide Number 22: Chemists" (http:/ / www. calmis. ca. gov/ file/ occguide/ CHEMIST. HTM). Calmis.ca.gov. 1999-10-29. . Retrieved 2011-06-12. [11] First chemists (http:/ / www. newscientist. com/ article/ mg16121734. 300-first-chemists. html), February 13, 1999, New Scientist [12] Alchemy Timeline (http:/ / www. chemheritage. org/ explore/ ancients-time. html) - Chemical Heritage Society [13] Lucretius (50 BCE). "de Rerum Natura (On the Nature of Things)" (http:/ / classics. mit. edu/ Carus/ nature_things. html). The Internet Classics Archive. Massachusetts Institute of Technology. . Retrieved 2007-01-09. [14] Simpson, David (29 June 2005). "Lucretius (c. 99 - c. 55 BCE)" (http:/ / www. iep. utm. edu/ l/ lucretiu. htm). The Internet History of Philosophy. . Retrieved 2007-01-09. [15] Richard Myers (2003). " The Basics of Chemistry (http:/ / books. google. com/ books?id=oS50J3-IfZsC& pg=PA13& dq& hl=en#v=onepage& q=& f=false)". Greenwood Publishing Group. pp.13–14. ISBN 0-313-31664-3 [16] Morris Kline (1985) Mathematics for the nonmathematician (http:/ / books. google. com/ books?id=f-e0bro-0FUC& pg=PA284& dq& hl=en#v=onepage& q=& f=false). Courier Dover Publications. p. 284. ISBN 0-486-24823-2

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[17] Will Durant (1980), The Age of Faith (The Story of Civilization, Volume 4), p. 162-186, Simon & Schuster, ISBN 0-671-01200-2 [18] Dr. K. Ajram (1992), Miracle of Islamic Science, Appendix B, Knowledge House Publishers, ISBN 0-911119-43-4.

"Humboldt regards the Muslims as the founders of chemistry." [19] Will Durant (1935): Our Oriental Heritage: Simon & Schuster:

"Something has been said about the chemical excellence of cast iron in ancient India, and about the high industrial development of the Gupta times, when India was looked to, even by Imperial Rome, as the most skilled of the nations in such chemical industries as dyeing, tanning, soap-making, glass and cement... By the sixth century the Hindus were far ahead of Europe in industrial chemistry; they were masters of calcination, distillation, sublimation, steaming, fixation, the production of light without heat, the mixing of anesthetic and soporific powders, and the preparation of metallic salts, compounds and alloys. The tempering of steel was brought in ancient India to a perfection unknown in Europe till our own times; King Porus is said to have selected, as a specially valuable gift from Alexander, not gold or silver, but thirty pounds of steel. The Moslems took much of this Hindu chemical science and industry to the Near East and Europe; the secret of manufacturing "Damascus" blades, for example, was taken by the Arabs from the Persians, and by the Persians from India."" [20] Eagle, Cassandra T.; Jennifer Sloan (1998). "Marie Anne Paulze Lavoisier: The Mother of Modern Chemistry" (http:/ / www. springerlink. com/ content/ x14v35m5n8822v42/ fulltext. pdf) (PDF). The Chemical Educator 3 (5): 1–18. doi:10.1007/s00897980249a. . Retrieved 2007-12-14. [21] "History - Robert Boyle (1627 - 1691)" (http:/ / www. bbc. co. uk/ history/ historic_figures/ boyle_robert. shtml). BBC. . Retrieved 2011-06-12. [22] Mi Gyung Kim (2003). Affinity, that Elusive Dream: A Genealogy of the Chemical Revolution. MIT Press. p. 440. ISBN 0262112736. [23] Ihde, Aaron John (1984). The Development of Modern Chemistry. Courier Dover Publications. p. 164. ISBN 0486642356. [24] Timeline of Element Discovery (http:/ / chemistry. about. com/ library/ weekly/ aa030303a. htm) - About.com [25] "History of Alchemy" (http:/ / www. alchemylab. com/ history_of_alchemy. htm). Alchemy Lab. . Retrieved 2011-06-12. [26] "alchemy", entry in The Oxford English Dictionary, J. A. Simpson and E. S. C. Weiner, vol. 1, 2nd ed., 1989, ISBN 0-19-861213-3. [27] p. 854, "Arabic alchemy", Georges C. Anawati, pp. 853-885 in Encyclopedia of the history of Arabic science, eds. Roshdi Rashed and Régis Morelon, London: Routledge, 1996, vol. 3, ISBN 0415124123. [28] Weekley, Ernest (1967). Etymological Dictionary of Modern English. New York: Dover Publications. ISBN 0486218732 [29] Strathern, P. (2000). Mendeleyev’s Dream – the Quest for the Elements. New York: Berkley Books. [30] Boyle, Robert (1661). The Sceptical Chymist. New York: Dover Publications, Inc. (reprint). ISBN 0486428257. [31] Glaser, Christopher (1663). Traite de la chymie. Paris. as found in: Kim, Mi Gyung (2003). Affinity, That Elusive Dream - A Genealogy of the Chemical Revolution. The MIT Press. ISBN 0-262-11273-6. [32] Stahl, George, E. (1730). Philosophical Principles of Universal Chemistry. London. [33] Dumas, J. B. (1837). 'Affinite' (lecture notes), vii, pg 4. “Statique chimique”, Paris: Academie des Sciences [34] Pauling, Linus (1947). General Chemistry. Dover Publications, Inc.. ISBN 0486656225. [35] Chang, Raymond (1998). Chemistry, 6th Ed.. New York: McGraw Hill. ISBN 0-07-115221-0. [36] "General Chemistry Online - Companion Notes: Matter" (http:/ / antoine. frostburg. edu/ chem/ senese/ 101/ matter/ ). Antoine.frostburg.edu. . Retrieved 2011-06-12. [37] Hill, J.W.; Petrucci, R.H.; McCreary, T.W.; Perry, S.S. (2005). General Chemistry (4th ed.). Upper Saddle River, NJ: Pearson Prentice Hall. p. 37. [38] "IUPAC Nomenclature of Organic Chemistry" (http:/ / www. acdlabs. com/ iupac/ nomenclature/ ). Acdlabs.com. . Retrieved 2011-06-12. [39] IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (http:/ / www. iupac. org/ reports/ provisional/ abstract04/ connelly_310804. html) [40] "Official SI Unit definitions" (http:/ / www. bipm. org/ en/ si/ base_units/ ). Bipm.org. . Retrieved 2011-06-12. [41] "The Lewis Acid-Base Concept" (http:/ / web. archive. org/ web/ 20080527132328/ http:/ / www. apsidium. com/ theory/ lewis_acid. htm). Apsidium. May 19, 2003. Archived from the original (http:/ / www. apsidium. com/ theory/ lewis_acid. htm) on 2008-05-27. . Retrieved 2010-07-31. [42] "History of Acidity" (http:/ / www. bbc. co. uk/ dna/ h2g2/ A708257). Bbc.co.uk. 2004-05-27. . Retrieved 2011-06-12. [43] Visionlearning. "Chemical Bonding by Anthony Carpi, Ph" (http:/ / www. visionlearning. com/ library/ module_viewer. php?mid=55). visionlearning. . Retrieved 2011-06-12. [44] Chemical Reaction Equation (http:/ / goldbook. iupac. org/ C01034. html)- IUPAC Goldbook [45] Gold Book Chemical Reaction (http:/ / goldbook. iupac. org/ C01033. html) IUPAC Goldbook [46] Reilly, Michael. (2007). Mechanical force induces chemical reaction (http:/ / www. newscientisttech. com/ article/ dn11427), NewScientist.com news service, Reilly [47] Changing States of Matter (http:/ / www. chem4kids. com/ files/ matter_changes. html) - Chemforkids.com

Chemistry [48] W.G. Laidlaw; D.E. Ryan And Gary Horlick; H.C. Clark, Josef Takats, And Martin Cowie; R.U. Lemieux (1986-12-10). "Chemistry Subdisciplines" (http:/ / www. thecanadianencyclopedia. com/ index. cfm?PgNm=TCE& Params=A1ARTA0001555). The Canadian Encyclopedia. . Retrieved 2011-06-12. [49] Herbst, Eric (May 12, 2005). "Chemistry of Star-Forming Regions". Journal of Physical Chemistry A 109 (18): 4017–4029. doi:10.1021/jp050461c. PMID 16833724. [50] "Top 50 Chemical Producers" (http:/ / pubs. acs. org/ cen/ coverstory/ 83/ 8329globaltop50. html). Chemical & Engineering News 83 (29): 20–23. July 18, 2005. .

Further reading Popular reading • Atkins, P.W. Galileo's Finger (Oxford University Press) ISBN 0-19-860941-8 • Atkins, P.W. Atkins' Molecules (Cambridge University Press) ISBN 0-521-82397-8 • Kean, Sam. The Disappearing Spoon - and other true tales from the Periodic Table (Black Swan) London, 2010 ISBN 978-0-552-77750-6 • Levi, Primo The Periodic Table (Penguin Books) [1975] translated from the Italian by Raymond Rosenthal (1984) ISBN 978-0-141-39944-7 • Stwertka, A. A Guide to the Elements (Oxford University Press) ISBN 0-19-515027-9 Introductory undergraduate text books • Atkins, P.W., Overton, T., Rourke, J., Weller, M. and Armstrong, F. Shriver and Atkins inorganic chemistry (4th edition) 2006 (Oxford University Press) ISBN 0-19-926463-5 • Chang, Raymond. Chemistry 6th ed. Boston: James M. Smith, 1998. ISBN 0-07-115221-0. • Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0. • Voet and Voet Biochemistry (Wiley) ISBN 0-471-58651-X Advanced undergraduate-level or graduate text books • • • • •

Atkins, P.W. Physical Chemistry (Oxford University Press) ISBN 0-19-879285-9 Atkins, P.W. et al. Molecular Quantum Mechanics (Oxford University Press) McWeeny, R. Coulson's Valence (Oxford Science Publications) ISBN 0-19-855144-4 Pauling, L. The Nature of the chemical bond (Cornell University Press) ISBN 0-8014-0333-2 Pauling, L., and Wilson, E. B. Introduction to Quantum Mechanics with Applications to Chemistry (Dover Publications) ISBN 0-486-64871-0 • Smart and Moore Solid State Chemistry: An Introduction (Chapman and Hall) ISBN 0-412-40040-5 • Stephenson, G. Mathematical Methods for Science Students (Longman) ISBN 0-582-44416-0 nso:Khemise

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History of chemistry

History of chemistry By 1000 BC, ancient civilizations used technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting metals from ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze. Early attempts to explain the nature of matter and its transformations failed. The protoscience of chemistry, Alchemy, was also unsuccessful in explaining the nature of matter. However, by performing experiments and recording the results the alchemist set the stage for modern chemistry. This distinction begins to emerge when a clear differentiation was made between chemistry and alchemy by Robert Boyle in his work The Sceptical Chymist (1661). Chemistry then becomes a full-fledged science when Antoine Lavoisier develops his law of conservation of mass, which demands careful measurements and quantitative observations of chemical phenomena. So, while both alchemy and chemistry are concerned with the nature of matter and its transformations, it is only the chemists who apply the scientific method. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs.[1]

From fire to atomism Arguably the first chemical reaction used in a controlled manner was fire. However, for millennia fire was simply a mystical force that could transform one substance into another (burning wood, or boiling water) while producing heat and light. Fire affected many aspects of early societies. These ranged from the most simple facets of everyday life, such as cooking and habitat lighting, to more advanced technologies, such as pottery, bricks, and melting of metals to make tools. Philosophical attempts to rationalize why different substances have different properties (color, density, smell), exist in different states (gaseous, liquid, and solid), and react in a different manner when exposed to environments, for example to water or fire or temperature changes, led ancient philosophers to postulate the first theories on nature and chemistry. The history of such philosophical theories that relate to chemistry, can probably be traced back to every single ancient civilization. The common aspect in all these theories was the attempt to identify a small number of primary elements that make up all the various substances in nature. Substances like air, water, and soil/earth, energy forms, such as fire and light, and more abstract concepts such as ideas, aether, and heaven, were common in ancient civilizations even in absence of any cross-fertilization; for example in Greek, Indian, Mayan, and ancient Chinese philosophies all considered air, water, earth and fire as primary elements. Atomism can be traced back to ancient Greece and ancient India.[2] Greek atomism dates back to 440 BC, as what might be indicated by the book De Rerum Natura (The Nature of Things)[3] written by the Roman Lucretius[4] in 50 BC. In the book was found ideas traced back to Democritus and Leucippus, who declared that atoms were the most indivisible part of matter. This coincided with a similar declaration by Indian philosopher Kanada in his Vaisheshika sutras around the same time period.[2] In much the same fashion he discussed the existence of gases. What Kanada declared by sutra, Democritus declared by philosophical musing. Both suffered from a lack of empirical data. Without scientific proof, the existence of atoms was easy to deny. Aristotle opposed the existence of atoms in 330 BC. Much of the early development of purification methods is described by Pliny the Elder in his Naturalis Historia. He made attempts to explain those methods, as well as making acute observations of the state of many minerals.

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History of chemistry

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The rise of metallurgy It was fire that led to the discovery of glass and the purification of metals which in turn gave way to the rise of metallurgy. During the early stages of metallurgy, methods of purification of metals were sought, and gold, known in ancient Egypt as early as 2600 BC, became a precious metal. The discovery of alloys heralded the Bronze Age. After the Bronze Age, the history of metallurgy was marked by which army had better weaponry. Countries in Eurasia had their heyday when they made the superior alloys, which, in turn, made better armour and better weapons. This often determined the outcomes of battles. Significant progress in metallurgy and alchemy was made in ancient India.[5]

The philosopher's stone and the rise of alchemy Many people were interested in finding a method that could convert cheaper metals into gold. The material that would help them do this was rumored to exist in what was called the philosopher's stone. This led to the protoscience called alchemy. Alchemy was practiced by many cultures throughout history and often contained a mixture of philosophy, mysticism, and protoscience.

"Renel the Alchemist", by Sir William Douglas, 1853

Alchemy not only sought to turn base metals into gold, but especially in a Europe rocked by bubonic plague, there was hope that alchemy would lead to the development of medicines to improve people's health. The holy grail of this strain of alchemy was in the attempts made at finding the elixir of life, which promised eternal youth. Neither the elixir nor the philosopher's stone were ever found. Also, characteristic of alchemists was the belief that there was in the air an "ether" which breathed life into living things. Practitioners of alchemy included Isaac Newton, who remained one throughout his life.

Problems encountered with alchemy There were several problems with alchemy, as seen from today's standpoint. There was no systematic naming system for new compounds, and the language was esoteric and vague to the point that the terminologies meant different things to different people. In fact, according to The Fontana History of Chemistry (Brock, 1992): The language of alchemy soon developed an arcane and secretive technical vocabulary designed to conceal information from the uninitiated. To a large degree, this language is incomprehensible to us today, though it is apparent that readers of Geoffery Chaucer's Canon's Yeoman's Tale or audiences of Ben Jonson's The Alchemist were able to construe it sufficiently to laugh at it.[6] Chaucer's tale exposed the more fraudulent side of alchemy, especially the manufacture of counterfeit gold from cheap substances. Less than a century earlier, Dante Alighieri also demonstrated an awareness of this fraudulence, causing him to consign all alchemists to the Inferno in his writings. Soon after, in 1317, the Avignon Pope John XXII ordered all alchemists to leave France for making counterfeit money. A law was passed in England in 1403 which made the "multiplication of metals" punishable by death. Despite these and other apparently extreme measures, alchemy did not die. Royalty and privileged classes still sought to discover the philosopher's stone and the elixir of life for themselves.[7] There was also no agreed-upon scientific method for making experiments reproducible. Indeed many alchemists included in their methods irrelevant information such as the timing of the tides or the phases of the moon. The

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esoteric nature and codified vocabulary of alchemy appeared to be more useful in concealing the fact that they could not be sure of very much at all. As early as the 14th century, cracks seemed to grow in the facade of alchemy; and people became sceptical. Clearly, there needed to be a scientific method where experiments can be repeated by other people, and results needed to be reported in a clear language that laid out both what is known and unknown.

From alchemy to chemistry

Ambix, cucurbit and retort of Zosimus, from Marcelin Berthelot, Collection des anciens alchimistes grecs (3 vol., Paris, 1887-1888).

Early chemists In the Arab World, the Muslims were translating the works of the ancient Greeks and Egyptians into Arabic and were experimenting with scientific ideas.[8] The development of the modern scientific method was slow and arduous, but an early scientific method for chemistry began emerging among early Muslim chemists, beginning with the 9th century chemist Jābir ibn Hayyān (known as "Geber" in Europe), who is "considered as the father of chemistry".[9] [10] [11] [12] He introduced a systematic and experimental approach to scientific research based in the laboratory, in contrast to the ancient Greek and Egyptian alchemists whose works were largely allegorical and often unintelligble.[13] He also invented and named the alembic (al-anbiq), chemically analyzed many chemical substances, composed lapidaries, distinguished between alkalis and acids, and manufactured hundreds of drugs.[14] He also refined the theory of five classical elements into the theory of seven alchemical elements after identifying mercury and sulfur as chemical elements.[15]

Jābir ibn Hayyān (Geber), a Persian alchemist whose experimental research laid the foundations for chemistry.

Among other influential Muslim chemists, Ja'far al-Sadiq,[16] Alkindus,[17] Abū al-Rayhān al-Bīrūnī,[18] Avicenna[19] and Ibn Khaldun refuted the theories of alchemy, particularly the theory of the transmutation of metals; and al-Tusi described a version of the conservation of mass, noting that a body of matter is able to change but is not able to disappear.[20] Rhazes refuted Aristotle's theory of four

History of chemistry

36

classical elements for the first time and set up the firm foundations of modern chemistry, using the laboratory in the modern sense, designing and describing more than twenty instruments, many parts of which are still in use today, such as a crucible, decensory, cucurbit or retort for distillation, and the head of a still with a delivery tube (ambiq, Latin alembic), and various types of furnace or stove. For the more honest practitioners in Europe, alchemy became an intellectual pursuit after early Arabic alchemy became available through Latin translation, and over time, they got better at it. Paracelsus (1493–1541), for example, rejected the 4-elemental theory and with only a vague understanding of his chemicals and medicines, formed a hybrid of alchemy and science in what was to be called iatrochemistry. Paracelsus was not perfect in making his experiments truly scientific. For example, as an extension of his theory that new compounds could be made by combining mercury with sulfur, he once made what he thought was "oil of sulfur". This was actually dimethyl ether, which had neither mercury nor sulfur. Practical attempts to improve the refining of ores and their extraction to smelt metals was an important source of information for early chemists, among them Georg Agricola (1494–1555), who published his great work De re Agricola, author of De re metallica metallica in 1556. His approach removed the mysticism associated with the subject, creating the practical base upon which others could build. The work describes the many kinds of furnace used to smelt ore, and stimulated interest in minerals and their composition. It is no coincidence that he gives numerous references to the earlier author, Pliny the Elder and his Naturalis Historia. In 1605, Sir Francis Bacon published The Proficience and Advancement of Learning, which contains a description of what would later be known as the scientific method.[21] In 1615 Jean Beguin publishes the Tyrocinium Chymicum, an early chemistry textbook, and in it draws the first-ever chemical equation.[22] Robert Boyle (1627–1691) is considered to have refined the modern scientific method for alchemy and to have separated chemistry further from alchemy.[23] Robert Boyle was an atomist, but favoured the word corpuscle over atoms. He comments that the finest division of matter where the properties are retained is at the level of corpuscles. Boyle was credited with the discovery of Boyle's Law. He is also credited for his landmark publication The Sceptical Chymist, where he attempts to develop an atomic theory of matter, with no small degree of success. He laid the foundations for the Chemical Revolution with his mechanical corpuscular philosophy, which in turn relied heavily on the alchemical corpuscular theory and experimental method dating back to the alchemist Jābir ibn Hayyān.[24] Despite all these advances, the person celebrated as the "father of modern chemistry" is Antoine Lavoisier who developed his law of conservation of mass in 1789, also called Lavoisier's Law.[25] With this, chemistry acquired a strict quantitative nature, allowing reliable predictions to be made.

Robert Boyle, one of the co-founders of modern chemistry through his use of proper experimentation, which further separated chemistry from alchemy

In 1754, Joseph Black isolated carbon dioxide, which he called "fixed air".[26] Carl Wilhelm Scheele and Joseph Priestley independently isolated oxygen, called by Priestley "dephlogisticated air" and Scheele "fire air".[27] [28]

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Joseph Proust proposed the law of definite proportions, which states that elements always combine in small, whole number ratios to form compounds.[29] In 1800, Alessandro Volta devised the first chemical battery, thereby founding the discipline of electrochemistry.[30] In 1803, John Dalton proposed Dalton's Law, which describes relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture.[31]

Antoine Lavoisier Although the archives of chemical research draw upon work from ancient Babylonia, Egypt, and especially the Arabs and Persians after Islam, modern chemistry flourished from the time of Antoine Lavoisier, who is regarded as the "father of modern chemistry", particularly for his discovery of the law of conservation of mass, and his refutation of the phlogiston theory of combustion in 1783. (Phlogiston was supposed to be an imponderable substance liberated by flammable materials in burning.) Mikhail Lomonosov independently established a tradition of chemistry in Russia in the 18th century. Lomonosov also rejected the phlogiston theory, and anticipated the kinetic theory of gases. He regarded heat as a form of motion, and stated the idea of conservation of matter.

The vitalism debate and organic chemistry After the nature of combustion (see oxygen) was settled, another dispute, about vitalism and the essential distinction between organic and inorganic substances, was revolutionized by Friedrich Wöhler's accidental synthesis of urea from inorganic substances in 1828. Never before had an organic compound been synthesized from inorganic material. This opened a new research field in chemistry, and by the end of the 19th century, scientists were able to synthesize hundreds of organic compounds. The most important among them are mauve, magenta, and other synthetic dyes, as well as the widely used drug aspirin. The discovery of the artificial synthesis of urea contributed greatly to the theory of isomerism, as the empirical chemical formulas for urea and ammonium cyanate are identical (see Wöhler synthesis). Portrait of Monsieur Lavoisier and his wife, by Jacques-Louis David

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Disputes about atomism after Lavoisier Throughout the 19th century, chemistry was divided between those who followed the atomic theory of John Dalton and those who did not, such as Wilhelm Ostwald and Ernst Mach.[32] Although such proponents of the atomic theory as Amedeo Avogadro and Ludwig Boltzmann made great advances in explaining the behavior of gases, this dispute was not finally settled until Jean Perrin's experimental investigation of Einstein's atomic explanation of Brownian motion in the first decade of the 20th century.[32] Well before the dispute had been settled, many had already applied the concept of atomism to chemistry. A major example was the ion theory of Svante Arrhenius which anticipated ideas about atomic substructure that did not fully develop until the 20th century. Michael Faraday was another early worker, whose major contribution to chemistry was electrochemistry, in which (among other things) a certain quantity of electricity during electrolysis or electrodeposition of metals was shown to be associated with certain quantities of chemical elements, and fixed quantities of the elements therefore with each other, in specific ratios. These findings, like those of Dalton's combining ratios, were early clues to the atomic nature of matter.

Bust of John Dalton by Chantrey

The periodic table

Dmitri Mendeleev, responsible for the periodic table.

For many decades, the list of known chemical elements had been steadily increasing. A great breakthrough in making sense of this long list (as well as in understanding the internal structure of atoms as discussed below) was Dmitri Mendeleev and Lothar Meyer's development of the periodic table, and particularly Mendeleev's use of it to predict the existence and the properties of germanium, gallium, and scandium, which Mendeleev called ekasilicon, ekaaluminium, and ekaboron respectively. Mendeleev made his prediction in 1870; gallium was discovered in 1875, and was found to have roughly the same properties that Mendeleev predicted for it.

The modern definition of chemistry Classically, before the 20th century, chemistry was defined as the science of the nature of matter and its transformations. It was therefore clearly distinct from physics which was not concerned with such dramatic transformation of matter. Moreover, in contrast to physics, chemistry was not using much of mathematics. Even some were particularly reluctant to using mathematics within chemistry. For example, Auguste Comte wrote in 1830: Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry.... if mathematical analysis should ever hold a prominent place in chemistry -- an aberration which is happily almost impossible -- it would occasion a rapid and widespread degeneration of that science. However, in the second part of the 19th century, the situation changed and August Kekule wrote in 1867:

History of chemistry I rather expect that we shall someday find a mathematico-mechanical explanation for what we now call atoms which will render an account of their properties. After the discovery by Ernest Rutherford and Niels Bohr of the atomic structure in 1912, and by Marie and Pierre Curie of radioactivity, scientists had to change their viewpoint on the nature of matter. The experience acquired by chemists was no longer pertinent to the study of the whole nature of matter but only to aspects related to the electron cloud surrounding the atomic nuclei and the movement of the latter in the electric field induced by the former (see Born-Oppenheimer approximation). The range of chemistry was thus restricted to the nature of matter around us in conditions which are not too far (or exceptionally far) from standard conditions for temperature and pressure and in cases where the exposure to radiation is not too different from the natural microwave, visible or UV radiations on Earth. Chemistry was therefore re-defined as the science of matter that deals with the composition, structure, and properties of substances and with the transformations that they undergo. However the meaning of matter used here relates explicitly to substances made of atoms and molecules, disregarding the matter within the atomic nuclei and its nuclear reaction or matter within highly ionized plasmas. This does not mean that chemistry is never involved with plasma or nuclear sciences or even bosonic fields nowadays, since areas such as Quantum Chemistry and Nuclear Chemistry are currently well developed and formally recognized sub-fields of study under the Chemical sciences (Chemistry), but what is now formally recognized as subject of study under the Chemistry category as a science is always based on the use of concepts that describe or explain phenomena either from matter or to matter in the atomic or molecular scale, including the study of the behavior of many molecules as an aggregate or the study of the effects of a single proton on a single atom, but excluding phenomena that deal with different (more "exotic") types of matter (e.g. Bose-Einstein condensate, Higgs Boson, dark matter, naked singularity, etc.) and excluding principles that refer to intrinsic abstract laws of nature in which their concepts can be formulated completely without a precise formal molecular or atomic paradigmatic view (e.g. Quantum Chromodynamics, Quantum Electrodynamics, String Theory, parts of Cosmology (see Cosmochemistry), certain areas of Nuclear Physics (see Nuclear Chemistry),etc.). Nevertheless the field of chemistry is still, on our human scale, very broad and the claim that chemistry is everywhere is accurate.

Quantum chemistry Some view the birth of quantum chemistry in the discovery of the Schrödinger equation and its application to the hydrogen atom in 1926. However, the 1927 article of Walter Heitler and Fritz London[33] is often recognised as the first milestone in the history of quantum chemistry.[34] This is the first application of quantum mechanics to the diatomic hydrogen molecule, and thus to the phenomenon of the chemical bond. In the following years much progress was accomplished by Edward Teller, Robert S. Mulliken, Max Born, J. Robert Oppenheimer, Linus Pauling, Erich Hückel, Douglas Hartree, Vladimir Aleksandrovich Fock, to cite a few. Still, skepticism remained as to the general power of quantum mechanics applied to complex chemical systems. The situation around 1930 is described by Paul Dirac:[35] The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation. Hence the quantum mechanical methods developed in the 1930s and 1940s are often referred to as theoretical molecular or atomic physics to underline the fact that they were more the application of quantum mechanics to chemistry and spectroscopy than answers to chemically relevant questions. In the 1940s many physicists turned from molecular or atomic physics to nuclear physics (like J. Robert Oppenheimer or Edward Teller). In 1951, a milestone article in quantum chemistry is the seminal paper of Clemens C. J. Roothaan on Roothaan equations.[36] It opened the avenue to the solution of the self-consistent field equations

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History of chemistry for small molecules like hydrogen or nitrogen. Those computations were performed with the help of tables of integrals which were computed on the most advanced computers of the time.

Molecular biology and biochemistry By the mid 20th century, in principle, the integration of physics and chemistry was extensive, with chemical properties explained as the result of the electronic structure of the atom; Linus Pauling's book on The Nature of the Chemical Bond used the principles of quantum mechanics to deduce bond angles in ever-more complicated molecules. However, though some principles deduced from quantum mechanics were able to predict qualitatively some chemical features for biologically relevant molecules, they were, till the end of the 20th century, more a collection of rules, observations, and recipes than rigorous ab initio quantitative methods. This heuristic approach triumphed in 1953 when James Watson and Francis Crick deduced the double helical structure of DNA by constructing models constrained by and informed by the knowledge of the chemistry of the constituent parts and the X-ray diffraction patterns obtained by Rosalind Franklin.[37] This discovery lead to an explosion of research into the biochemistry of life. In the same year, the Miller-Urey experiment demonstrated that basic constituents of protein, simple amino acids, could themselves be built up from simpler molecules in a simulation of primordial processes on Earth. Though many questions remain about the true nature of the origin of life, this was the first attempt by chemists to study hypothetical processes in the laboratory under controlled conditions. Diagrammatic representation of some key structural In 1983 Kary Mullis devised a method for the in-vitro features of DNA amplification of DNA, known as the polymerase chain reaction (PCR), which revolutionized the chemical processes used in the laboratory to manipulate it. PCR could be used to synthesize specific pieces of DNA and made possible the sequencing of DNA of organisms, which culminated in the huge human genome project.

An important piece in the double helix puzzle was solved by one of Pauling's student Matthew Meselson and Frank Stahl, the result of their collaboration (Meselson-Stahl experiment) has been called as "the most beautiful experiment in biology". They used a centrifugation technique that sorted molecules according to differences in weight. Because nitrogen atoms are a component of DNA, they were labelled and therefore tracked in replication in bacteria.

Chemical industry The later part of the nineteenth century saw a huge increase in the exploitation of petroleum extracted from the earth for the production of a host of chemicals and largely replaced the use of whale oil, coal tar and naval stores used previously. Large scale production and refinement of petroleum provided feedstocks for liquid fuels such as gasoline and diesel, solvents, lubricants, asphalt, waxes, and for the production of many of the common materials of the modern world, such as synthetic fibers, plastics, paints, detergents, pharmaceuticals, adhesives and ammonia as fertilizer and for other uses. Many of these required new catalysts and the utilization of chemical engineering for their cost-effective production. In the mid-twentieth century, control of the electronic structure of semiconductor materials was made precise by the creation of large ingots of extremely pure single crystals of silicon and germanium. Accurate control of their

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History of chemistry chemical composition by doping with other elements made the production of the solid state transistor in 1951 and made possible the production of tiny integrated circuits for use in electronic devices, especially computers.

Notes [1] Selected Classic Papers from the History of Chemistry (http:/ / web. lemoyne. edu/ ~giunta/ papers. html) [2] Will Durant (1935), Our Oriental Heritage:

"Two systems of Hindu thought propound physical theories suggestively similar to those of Greece. Kanada, founder of the Vaisheshika philosophy, held that the world was composed of atoms as many in kind as the various elements. The Jains more nearly approximated to Democritus by teaching that all atoms were of the same kind, producing different effects by diverse modes of combinations. Kanada believed light and heat to be varieties of the same substance; Udayana taught that all heat comes from the sun; and Vachaspati, like Newton, interpreted light as composed of minute particles emitted by substances and striking the eye." [3] Lucretius (50 BCE). "de Rerum Natura (On the Nature of Things)" (http:/ / classics. mit. edu/ Carus/ nature_things. html). The Internet Classics Archive. Massachusetts Institute of Technology. . Retrieved 2007-01-09. [4] Simpson, David (29 June 2005). "Lucretius (c. 99 - c. 55 BCE)" (http:/ / www. iep. utm. edu/ l/ lucretiu. htm). The Internet History of Philosophy. . Retrieved 2007-01-09. [5] Will Durant wrote in The Story of Civilization I: Our Oriental Heritage:

"Something has been said about the chemical excellence of cast iron in ancient India, and about the high industrial development of the Gupta times, when India was looked to, even by Imperial Rome, as the most skilled of the nations in such chemical industries as dyeing, tanning, soap-making, glass and cement... By the sixth century the Hindus were far ahead of Europe in industrial chemistry; they were masters of calcinations, distillation, sublimation, steaming, fixation, the production of light without heat, the mixing of anesthetic and soporific powders, and the preparation of metallic salts, compounds and alloys. The tempering of steel was brought in ancient India to a perfection unknown in Europe till our own times; King Porus is said to have selected, as a specially valuable gift from Alexander, not gold or silver, but thirty pounds of steel. The Moslems took much of this Hindu chemical science and industry to the Near East and Europe; the secret of manufacturing "Damascus" blades, for example, was taken by the Arabs from the Persians, and by the Persians from India." [6] [7] [8] [9]

Brock, William H. (1992). The Fontana History of Chemistry. London, England: Fontana Press. pp. 32–33. ISBN 0006861733. Brock, William H. (1992). The Fontana History of Chemistry. London, England: Fontana Press. ISBN 0006861733. The History of Ancient Chemistry (http:/ / realscience. breckschool. org/ upper/ fruen/ files/ Enrichmentarticles/ files/ History. html) Derewenda, ZS (2007). "On wine, chirality and crystallography". Acta Crystallographica Section A: Foundations of Crystallography 64 (Pt 1): 246–258 [247]. doi:10.1107/S0108767307054293. PMID 18156689. [10] John Warren (2005). "War and the Cultural Heritage of Iraq: a sadly mismanaged affair", Third World Quarterly, Volume 26, Issue 4 & 5, p. 815-830. [11] Dr. A. Zahoor (1997), JABIR IBN HAIYAN (Jabir) (http:/ / www. unhas. ac. id/ ~rhiza/ saintis/ haiyan. html), University of Indonesia [12] Paul Vallely, How Islamic inventors changed the world (http:/ / news. independent. co. uk/ world/ science_technology/ article350594. ece), The Independent [13] Kraus, Paul, Jâbir ibn Hayyân, Contribution à l'histoire des idées scientifiques dans l'Islam. I. Le corpus des écrits jâbiriens. II. Jâbir et la science grecque,. Cairo (1942-1943). Repr. By Fuat Sezgin, (Natural Sciences in Islam. 67-68), Frankfurt. 2002:

“To form an idea of the historical place of Jabir’s alchemy and to tackle the problem of its sources, it is advisable to compare it with what remains to us of the alchemical literature in the Greek language. One knows in which miserable state this literature reached us. Collected by Byzantine scientists from the tenth century, the corpus of the Greek alchemists is a cluster of incoherent fragments, going back to all the times since the third century until the end of the Middle Ages.” “The efforts of Berthelot and Ruelle to put a little order in this mass of literature led only to poor results, and the later researchers, among them in particular Mrs. Hammer-Jensen, Tannery, Lagercrantz , von Lippmann, Reitzenstein, Ruska, Bidez, Festugiere and others, could make clear only few points of detail…

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History of chemistry The study of the Greek alchemists is not very encouraging. An even surface examination of the Greek texts shows that a very small part only was organized according to true experiments of laboratory: even the supposedly technical writings, in the state where we find them today, are unintelligible nonsense which refuses any interpretation. It is different with Jabir’s alchemy. The relatively clear description of the processes and the alchemical apparatuses, the methodical classification of the substances, mark an experimental spirit which is extremely far away from the weird and odd esotericism of the Greek texts. The theory on which Jabir supports his operations is one of clearness and of an impressive unity. More than with the other Arab authors, one notes with him a balance between theoretical teaching and practical teaching, between the `ilm and the `amal. In vain one would seek in the Greek texts a work as systematic as that which is presented for example in the Book of Seventy.” (cf. Ahmad Y Hassan. "A Critical Reassessment of the Geber Problem: Part Three" (http:/ / www. history-science-technology. com/ Geber/ Geber 3. htm). . Retrieved 2008-08-09.) [14] Will Durant (1980). The Age of Faith (The Story of Civilization, Volume 4), p. 162-186. Simon & Schuster. ISBN 0671012002. [15] Strathern, Paul. (2000), Mendeleyev’s Dream – the Quest for the Elements, New York: Berkley Books [16] Research Committee of Strasburg University, Imam Jafar Ibn Muhammad As-Sadiq A.S. The Great Muslim Scientist and Philosopher, translated by Kaukab Ali Mirza, 2000. Willowdale Ont. ISBN 0969949014. [17] Felix Klein-Frank (2001), "Al-Kindi", in Oliver Leaman & Hossein Nasr, History of Islamic Philosophy, p. 174. London: Routledge. [18] Marmura Michael E., Nasr Seyyed Hossein (1965). "An Introduction to Islamic Cosmological Doctrines. Conceptions of Nature and Methods Used for Its Study by the Ikhwan Al-Safa'an, Al-Biruni, and Ibn Sina by Seyyed Hossein Nasr". Speculum 40 (4): 744–746. doi:10.2307/2851429. JSTOR 2851429. [19] Robert Briffault (1938). The Making of Humanity, p. 196-197. [20] Alakbarov Farid (2001). "A 13th-Century Darwin? Tusi's Views on Evolution" (http:/ / azer. com/ aiweb/ categories/ magazine/ 92_folder/ 92_articles/ 92_tusi. html). Azerbaijan International 9: 2. . [21] Asarnow, Herman (2005-08-08). "Sir Francis Bacon: Empiricism" (http:/ / faculty. up. edu/ asarnow/ eliz4. htm). An Image-Oriented Introduction to Backgrounds for English Renaissance Literature. University of Portland. . Retrieved 2007-02-22. [22] Crosland, M.P. (1959). "The use of diagrams as chemical 'equations' in the lectures of William Cullen and Joseph Black." Annals of Science, Vol 15, No. 2, Jun. [23] Robert Boyle (http:/ / understandingscience. ucc. ie/ pages/ sci_robertboyle. htm) [24] Ursula Klein (July 2007). "Styles of Experimentation and Alchemical Matter Theory in the Scientific Revolution". Metascience (Springer) 16 (2): 247–256 [247]. doi:10.1007/s11016-007-9095-8. ISSN 1467-9981 [25] Lavoisier, Antoine (1743-1794) -- from Eric Weisstein's World of Scientific Biography (http:/ / scienceworld. wolfram. com/ biography/ Lavoisier. html), ScienceWorld [26] Cooper, Alan (1999). "Joseph Black" (http:/ / web. archive. org/ web/ 20060410074412/ http:/ / www. chem. gla. ac. uk/ dept/ black. htm). History of Glasgow University Chemistry Department. University of Glasgow Department of Chemistry. Archived from the original (http:/ / www. chem. gla. ac. uk/ dept/ black. htm) on 2006-04-10. . Retrieved 2006-02-23. [27] "Joseph Priestley" (http:/ / www. chemheritage. org/ classroom/ chemach/ forerunners/ priestley. html). Chemical Achievers: The Human Face of Chemical Sciences. Chemical Heritage Foundation. 2005. . Retrieved 2007-02-22. [28] "Carl Wilhelm Scheele" (http:/ / mattson. creighton. edu/ History_Gas_Chemistry/ Scheele. html). History of Gas Chemistry. Center for Microscale Gas Chemistry, Creighton University. 2005-09-11. . Retrieved 2007-02-23. [29] "Proust, Joseph Louis (1754-1826)" (http:/ / www. euchems. org/ Distinguished/ 19thCentury/ proustlouis. asp). 100 Distinguished Chemists. European Association for Chemical and Molecular Science. 2005. . Retrieved 2007-02-23. [30] "Inventor Alessandro Volta Biography" (http:/ / www. ideafinder. com/ history/ inventors/ volta. htm). The Great Idea Finder. The Great Idea Finder. 2005. . Retrieved 2007-02-23. [31] "John Dalton" (http:/ / www. chemheritage. org/ classroom/ chemach/ periodic/ dalton. html). Chemical Achievers: The Human Face of Chemical Sciences. Chemical Heritage Foundation. 2005. . Retrieved 2007-02-22. [32] Pullman, Bernard (2004). The Atom in the History of Human Thought. Reisinger, Axel. USA: Oxford University Press Inc. ISBN 0195114477. [33] W. Heitler and F. London, Wechselwirkung neutraler Atome und Homöopolare Bindung nach der Quantenmechanik, Z. Physik, 44, 455 (1927). [34] Quantum chemistry (http:/ / www. fact-archive. com/ encyclopedia/ Quantum_chemistry) [35] P.A.M. Dirac, Quantum Mechanics of Many-Electron Systems, Proc. R. Soc. London, A 123, 714 (1929). [36] C.C.J. Roothaan, A Study of Two-Center Integrals Useful in Calculations on Molecular Structure, J. Chem. Phys., 19, 1445 (1951). [37] Watson, J. and Crick, F., "Molecular Structure of Nucleic Acids" (http:/ / www. nature. com/ nature/ dna50/ watsoncrick. pdf) Nature, April 25, 1953, p 737–8

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References • Selected classic papers from the history of chemistry (http://web.lemoyne.edu/~giunta/papers.html) • Biographies of chemists (http://www.liv.ac.uk/Chemistry/Links/refbiog.html) • Eric R. Scerri, The Periodic Table: Its Story and Its Significance, Oxford University Press, 2006.

Further reading • Servos, John W., Physical chemistry from Ostwald to Pauling : the making of a science in America (http://books. google.com/books?id=1UZjU2WfLAoC&printsec=frontcover), Princeton, N.J. : Princeton University Press, 1990. ISBN 0691085668 Documentaries • BBC (2010). Chemistry: A Volatile History.

External links • ChemisLab (http://www.chemislab.com/chemists-of-the-past/) - Chemists of the Past • SHAC: Society for the History of Alchemy and Chemistry (http://www.ambix.org/)

Alchemy and chemistry in medieval Islam Alchemy and chemistry in Islam refers to the study of both traditional alchemy and early practical chemistry (the early chemical investigation of nature in general) by scholars in the medieval Islamic world. The word alchemy was derived from the Arabic word ‫ ﻛﻴﻤﻴﺎء‬or kīmīāʾ. [1] [2] and may ultimately derive from the ancient Egyptian word kemi, meaning black.[2] After the fall of the Western Roman Empire, the focus of alchemical development moved to the Arab Empire and the Islamic civilization. Much more is known about Islamic alchemy as it was better documented; most of the earlier writings that have come down through the years were preserved as Arabic translations.[3]

Origins Medieval Islamic alchemy was based on previous alchemical writers, firstly those writing in Greek, but also using Indian, Jewish, and Christian sources. According to Anawati, the alchemy practiced in Egypt around the second century BCE was a mixture of Hermetic or gnostic elements and Greek philosophy. Later, with Zosimos of Panopolis, alchemy acquired mystical and religious elements.[4] The sources of Islamic alchemy were transmitted to the Muslim world mainly in Egypt, especially in Alexandria, but also in the cities of Harran, Nisibin, and Edessa in western Mesopotamia.[5]

Alchemists and works Khālid ibn Yazīd According to the biographer Ibn al-Nadīm, the first Muslim alchemist was Khālid ibn Yazīd, who is said to have studied alchemy under the Christian Marianos of Alexandria. The historicity of this story is not clear; according to M. Ullmann, it is a legend.[6] [7] According to Ibn al-Nadīm and Ḥajji Khalīfa, he is the author of the alchemical works Kitāb al-kharazāt (The Book of Pearls), Kitāb al-ṣaḥīfa al-kabīr (The Big Book of the Roll), Kitāb al-ṣaḥīfa al-saghīr (The Small Book of the Roll), Kitāb Waṣiyyatihi ilā bnihi fī-l-ṣanʿa (The Book of his Testament to his Son about Alchemy), and Firdaws al-ḥikma (The Paradise of Wisdom), but again, these works may be

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Alchemy and chemistry in medieval Islam

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pseudepigraphical.[8] [7] [6]

Jaʿfar al-Ṣādiq Jaʿfar al-Ṣādiq, the son of Muḥammad al-Bāqir, lived in Medina. He is said to have been the teacher of Jābir ibn Ḥayyān. A number of pseudepigraphical works have been attributed to him.[8]

Jābir ibn Ḥayyān Jābir ibn Ḥayyān (Persian: ‫ﺟﺎﺑﺮ ﺑﻦ ﺣﯿﺎﻥ‬, Latin Geberus; usually rendered in English as Geber) may have been born in 721 or 722, in Tus, and have been the son of Ḥayyan, a druggist from the tribe of al-Azd who originally lived in Kufa. When young Jābir studied in Arabia under Harbi al-Himyari. Later, he lived in Kufa, and eventually became a court alchemist for Hārūn al-Rashīd, in Baghdad. Jābir was friendly with the Barmecides and became caught up in their disgrace in 803. As a result, he returned to Kufa. According to some sources, he died in Tus in 815. A large corpus of works is ascribed to Jābir, so large that it's difficult to believe he wrote them all himself. According to the theory of Kraus, many of these works should be ascribed to later Ismaili authors. It includes the following groups of works: The Hundred and Twelve Books; The Seventy Books; The Ten Books of Rectifications; and The Books of the Balances. This article will not distinguish between Jābir and the authors of works attributed to him.[9]

15th century European impression of "Geber"

Muhammad ibn Jarir al-Tabari Abu Ja'far Muhammad ibn Jarir al-Tabari (Persian: ‫ ;ﻣﺤﻤﺪ ﺑﻦ ﺟﺮﯾﺮ ﻃﺒﺮﯼ‬Muḥammad b.Ǧarīr aṭ-Ṭabarī, Arabic: ‫ﺃﺑﻮ ﺟﻌﻔﺮ‬ ‫ ;ﻣﺤﻤﺪ ﺑﻦ ﺟﺮﻳﺮ ﺑﻦ ﻳﺰﻳﺪ ﺍﻟﻄﺒﺮﻱ‬Abū Ǧaʿfar Muḥammad b.Ǧarīr b.Yazīd aṭ-Ṭabarī) (838–923) 224 – 310H, was one of the earliest, most prominent and famous Persian[1][2][3][4][5] historian and exegete of the Qur'an, most famous for his (‫ )ﺗﺎﺭﻳﺦ ﺍﻟﺮﺳﻞ ﻭﺍﻟﻤﻠﻮﻙ‬Tarikh al-Rusul wa al-Mulouk, or abbreviated as: "Tarikh al-Tabari" and Tafsir al-Tabari.

Abū Bakr al-Rāzī Abū Bakr al-Rāzī (Latin: Rhazes), born around 864 in Rey, was mainly known as a doctor. He wrote a number of alchemical works, including Sirr al-asrār (Latin: Secretum secretorum.)[10] [11]

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Ibn Umayl Muḥammad ibn Umayl al-Tamīmī was an 11th-century alchemist. One of his surviving works is Kitāb al-māʿ al-waraqī wa-l-arḍ al-najmiyya (The Book on Silvered Water and Starry Earth.) This work is a commentary on his poem Risālat al-shams wa-t-hilāl (The Epistle on the Sun and the Crescent) and contains numerous quotations from ancient authors.[12]

Alchemical and chemical theory Elemental scheme used by Jābir[13] Hot Cold Dry

Fire Earth

Moist Air

Water

Jābir analyzed each Aristotelian element in terms of four basic qualities of hotness, coldness, dryness, and moistness. For example, fire is a substance that is hot and dry, as shown in the table.[13] (This scheme was also used by Aristotle.)[14] [15] According to Jābir, in each metal two of these qualities were interior and two were exterior. For example, lead was externally cold and dry but internally hot and moist; gold, on the other hand, was externally hot and moist but internally cold and dry. He believed that metals were formed in the Earth by fusion of sulfur (giving the hot and dry qualities) with mercury (giving the cold and moist.) These elements, mercury and sulfur, should be thought of as not the ordinary elements but ideal, hypothetical substances. Which metal is formed depends on the purity of the mercury and sulfur and the proportion in which they come together.[13] The later alchemist al-Rāzī followed Jābir's mercury-sulfur theory, but added a third, salty, component.[16] Thus, Jābir theorized, by rearranging the qualities of one metal, a different metal would result.[17] By this reasoning, the search for the philosopher's stone was introduced to Western alchemy.[18] [19] Jābir developed an elaborate numerology whereby the root letters of a substance's name in Arabic, when treated with various transformations, held correspondences to the element's physical properties.[13]

Processes and equipment Al-Rāzī mentions the following chemical processes: • • • • • • • • •

distillation, calcination, solution, evaporation, crystallization, sublimation, filtration, amalgamation, and ceration (a process for making solids pasty or fusible.)[20]

Some of these operations (calcination, solution, filtration, crystallization, sublimation and distillation) are also known to have been practiced by pre-Islamic Alexandrian alchemists.[21] In his Secretum secretorum, Al-Rāzī mentions the following equipment:[22] • Tools for melting substances (li-tadhwīb): hearth (kūr), bellows (minfākh aw ziqq), crucible (bawtaqa), the būt bar būt (in Arabic) or botus barbatus (in Latin), ladle (mighrafa aw milʿaqa), tongs (māsik aw kalbatān), scissors (miqṭaʿ), hammer (mukassir), file (mibrad).

Alchemy and chemistry in medieval Islam • Tools for the preparation of drugs (li-tadbīr al-ʿaqāqīr): cucurbit and still with evacuation tube (qarʿ aw anbīq dhū-khatm), receiving matras (qābila), blind still (without evacuation tube) (al-anbīq al-aʿmā), aludel (al-uthāl), goblets (qadaḥ), flasks (qārūra, plural quwārīr), rosewater flasks (māʿ wariyya), cauldron (marjal aw tanjīr), earthenware pots varnished on the inside with their lids (qudūr wa makabbāt), water bath or sand bath (qadr), oven (al-tannūr in Arabic, athanor in Latin), small cylindirical oven for heating aludel (mustawqid), funnels, sieves, filters, etc.

References [1] "alchemy", entry in The Oxford English Dictionary, J. A. Simpson and E. S. C. Weiner, vol. 1, 2nd ed., 1989, ISBN 0-19-861213-3. [2] p. 854, "Arabic alchemy", Georges C. Anawati, pp. 853-885 in Encyclopedia of the history of Arabic science, eds. Roshdi Rashed and Régis Morelon, London: Routledge, 1996, vol. 3, ISBN 0415124123. [3] Burckhardt, Titus (1967). Alchemy: science of the cosmos, science of the soul. Stuart & Watkins. p. 46 [4] Anawati 1996, pp. 854-863. [5] pp. 67-68, Holmyard 1990. [6] pp. 63-66, Alchemy, E. J. Holmyard, New York: Dover Publications, Inc., 1990 (reprint of 1957 Penguin Books edition), ISBN 0-486-26298-7. [7] M. Ullmann, "Ḵh̲ālid b. Yazīd b. Muʿāwiya, abū hās̲h̲im.", in Encyclopaedia of Islam, second edition, edited by P. Bearman, Th. Bianquis, C. E. Bosworth, E. van Donzel, and W.P. Heinrichs, Brill, 2011. Brill Online. Accessed 20 January 2011. [8] Anawati 1996, p. 864. [9] pp. 68-82, Holmyard 1990. [10] pp. 867-879, Anawati 1996. [11] pp. 86-92, Holmyard 1990. [12] pp. 870-872, Anawati 1996. [13] pp. 74-82, Holmyard 1990. [14] Holmyard 1990, pp. 21-22. [15] Aristotle, On Generation and Corruption, II.3, 330a-330b. [16] Holmyard 1990, p. 88. [17] Burckhardt, Titus (1967). Alchemy: science of the cosmos, science of the soul. Stuart & Watkins. p. 29 [18] Ragai, Jehane (1992). "The Philosopher's Stone: Alchemy and Chemistry". Journal of Comparative Poetics 12 (Metaphor and Allegory in the Middle Ages): 58–77 [19] Holmyard, E. J. (1924). "Maslama al-Majriti and the Rutbatu'l-Hakim". Isis 6 (3): 293–305 [20] p. 89, Holmyard 1990. [21] p. 23, A short history of chemistry, James Riddick Partington, 3rd ed., Courier Dover Publications, 1989, ISBN 0486659771. [22] Anawati 1996, p. 868

External links • "How Greek Science Passed to the Arabs" (http://www.aina.org/books/hgsptta.htm) by De Lacy O'Leary

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Timeline of chemistry

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Timeline of chemistry The timeline of chemistry lists important works, discoveries, ideas, inventions, and experiments that significantly changed humanity's understanding of the modern science known as chemistry, defined as the scientific study of the composition of matter and of its interactions. The history of chemistry in its modern form arguably began with the English scientist Robert Boyle, though its roots can be traced back to the earliest recorded history. Early ideas that later became incorporated into the modern science of chemistry come from two main sources. Natural philosophers (such as Aristotle and Democritus) used deductive reasoning in an attempt to explain the behavior of the world around them. Alchemists (such as Geber and Rhazes) were people who used experimental techniques in an attempt to extend the life or perform material conversions, such as turning base metals into gold. In the 17th century, a synthesis of the ideas of these two disciplines, that is the deductive and the experimental, leads to the development of a process of thinking known as the scientific method. With the introduction of the scientific method, the modern science of chemistry was born. An image from John Dalton's A New System of

Known as "the central science", the study of chemistry is strongly Chemical Philosophy, the first modern influenced by, and exerts a strong influence on, many other scientific explanation of atomic theory. and technological fields. Many events considered central to our modern understanding of chemistry are also considered key discoveries in such fields as physics, biology, astronomy, geology, and materials science to name a few.[1]

Pre-17th century Prior to the acceptance of the scientific method and its application to the field of chemistry, it is somewhat controversial to consider many of the people listed below as "chemists" in the modern sense of the word. However, the ideas of certain great thinkers, either for their prescience, or for their wide and long-term acceptance, bear listing here. c. 3000 BCE Egyptians formulate the theory of the Ogdoad, or the “primordial forces”, from which all was formed. These were the elements of chaos, numbered in eight, that existed before the creation of the sun.[2] c. 1900 BCE Hermes Trismegistus, semi-mythical ancient Egyptian adept king, is thought to have founded the art of alchemy.[3] c. 1200 BCE

Aristotle (384–322 BCE)

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Tapputi-Belatikallim, a perfume-maker and early chemist, was mentioned in a cuneiform tablet in Mesopotamia.[4] c. 450 BCE Empedocles asserts that all things are composed of four primal elements: earth, air, fire, and water, whereby two active and opposing forces, love and hate, or affinity and antipathy, act upon these elements, combining and separating them into infinitely varied forms.[5] c. 440 BCE Leucippus and Democritus propose the idea of the atom, an indivisible particle that all matter is made of. This idea is largely rejected by natural philosophers in favor of the Aristotlean view.[6] [7]

Ambix, cucurbit and retort, the alchemical implements of Zosimus c. 300, from Marcelin Berthelot, Collection des anciens alchimistes grecs (3 vol., Paris, 1887–88)

c. 360 BCE Plato coins term ‘elements’ (stoicheia) and in his dialogue Timaeus, which includes a discussion of the composition of inorganic and organic bodies and is a rudimentary treatise on chemistry, assumes that the minute particle of each element had a special geometric shape: tetrahedron (fire), octahedron (air), icosahedron (water), and cube (earth).[8] c. 350 BCE Aristotle, expanding on Empedocles, proposes idea of a substance as a combination of matter and form. Describes theory of the Five Elements, fire, water, earth, air, and aether. This theory is largely accepted throughout the western world for over 1000 years.[9]

Geber (d. 815) is considered by some to be the "father of chemistry".

c. 50 BCE Lucretius publishes De Rerum Natura, a poetic description of the ideas of Atomism.[10] c. 300 Zosimos of Panopolis writes some of the oldest known books on alchemy, which he defines as the study of the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and bonding the spirits within bodies.[11] c. 770 Abu Musa Jabir ibn Hayyan (aka Geber), an Arab/Persian alchemist who is "considered by many to be the father of chemistry",[12] [13] [14] develops an early experimental method for chemistry, and isolates numerous acids, including hydrochloric acid, nitric acid, citric acid, acetic acid, tartaric acid, and aqua regia.[15] c. 1000 Abū al-Rayhān al-Bīrūnī[16] and Avicenna,[17] both Persian chemists, refute the practice of alchemy and the theory of the transmutation of metals. c. 1167 Alchemists in the School of Salerno make the first references to the distillation of wine.[18] c. 1220

Timeline of chemistry Robert Grosseteste publishes several Aristotelian commentaries where he lays out an early framework for the scientific method.[19] c 1250 Tadeo Alderotti develops Fractional distillation, which is much more effective than its predecessors.[20] c 1260 St Albertus Magnus discovers Arsenic[21] and Silver nitrate.[22] He also made one of the first references to sulfuric acid.[23] c. 1267 Roger Bacon publishes Opus Maius, which among other things, proposes an early form of the scientific method, and contains results of his experiments with gunpowder.[24] c. 1310 Pseudo-Geber, an anonymous Spanish alchemist who wrote under the name of Geber, publishes several books that establish the long-held theory that all metals were composed of various proportions of sulfur and mercury.[25] He is one of the first to describe nitric acid, aqua regia, and aqua fortis.[26] c. 1530 Paracelsus develops the study of iatrochemistry, a subdiscipline of alchemy dedicated to extending the life, thus being the roots of the modern pharmaceutical industry. It is also claimed that he is the first to use the word "chemistry".[11] 1597 Andreas Libavius publishes Alchemia, a prototype chemistry textbook.[27]

17th and 18th centuries 1605 Sir Francis Bacon publishes The Proficience and Advancement of Learning, which contains a description of what would later be known as the scientific method.[28] 1605 Michal Sedziwój publishes the alchemical treatise A New Light of Alchemy which proposed the existence of the "food of life" within air, much later recognized as oxygen.[29] 1615 Jean Beguin publishes the Tyrocinium Chymicum, an early chemistry textbook, and in it draws the first-ever chemical equation.[30] 1637 René Descartes publishes Discours de la méthode, which contains an outline of the scientific method.[31] 1648 Posthumous publication of the book Ortus medicinae by Jan Baptist van Helmont, which is cited by some as a major transitional work between alchemy and chemistry, and as an important influence on Robert Boyle. The book contains the results of numerous experiments and establishes an early version of the Law of conservation of mass.[32]

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1661 Robert Boyle publishes The Sceptical Chymist, a treatise on the distinction between chemistry and alchemy. It contains some of the earliest modern ideas of atoms, molecules, and chemical reaction, and marks the beginning of the history of modern chemistry.[33] 1662 Robert Boyle proposes Boyle's Law, an experimentally based description of the behavior of gases, specifically the relationship between pressure and volume.[33] 1735 Swedish chemist Georg Brandt analyzes a dark blue pigment found in copper ore. Brandt demonstrated that the pigment contained a new element, later named cobalt. Title page of The Sceptical Chymist by Robert Boyle (1627–91)

1754 Joseph Black isolates carbon dioxide, which he called "fixed air".[34] 1757 Louis Claude Cadet de Gassicourt, while investigating arsenic compounds, creates Cadet's fuming liquid, later discovered to be Cacodyl oxide, considered to be the first synthetic organometallic compound.[35] 1758 Joseph Black formulates the concept of latent heat to explain the thermochemistry of phase changes.[36]

A typical chemical laboratory of the 18th century

1766 Henry Cavendish discovers hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air. 1773–1774 Carl Wilhelm Scheele and Joseph Priestly independently isolate oxygen, called by Priestly "dephlogisticated air" and Scheele "fire air".[37] [38]

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1778 Antoine Lavoisier, considered "The father of modern chemistry",[39] recognizes and names oxygen, and recognizes its importance and role in combustion.[40] 1787 Antoine Lavoisier publishes Méthode de nomenclature chimique, the first modern system of chemical nomenclature.[40] 1787 Jacques Charles proposes Charles's Law, a corollary of Boyle's Law, describes relationship between temperature and volume of a gas.[41] 1789 Antoine Lavoisier publishes Traité Élémentaire de Chimie, the first modern chemistry textbook. It is a complete survey of (at that time) modern chemistry, including the first concise definition of the law of conservation of mass, and thus also represents the founding of the discipline of stoichiometry or quantitative chemical analysis.[40] [42]

Antoine-Laurent de Lavoisier (1743–94) is considered the "Father of Modern Chemistry".

1797 Joseph Proust proposes the law of definite proportions, which states that elements always combine in small, whole number ratios to form compounds.[43] 1800 Alessandro Volta devises the first chemical battery, thereby founding the discipline of electrochemistry.[44]

19th century 1803 John Dalton proposes Dalton's Law, which describes relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture.[45] 1805 Joseph Louis Gay-Lussac discovers that water is composed of two parts hydrogen and one part oxygen by volume.[46] 1808 Joseph Louis Gay-Lussac collects and discovers several chemical and physical properties of air and of other gases, including experimental proofs of Boyle's and Charles's laws, and of relationships between density and composition of gases.[47] 1808 John Dalton publishes New System of Chemical Philosophy, which contains first modern scientific description of the atomic theory, and clear description of the law of multiple proportions.[45]

John Dalton (1766–1844)

1808 Jöns Jakob Berzelius publishes Lärbok i Kemien in which he proposes modern chemical symbols and notation, and of the concept of relative atomic weight.[48]

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1811 Amedeo Avogadro proposes Avogadro's law, that equal volumes of gases under constant temperature and pressure contain equal number of molecules.[49] 1825 Friedrich Wöhler and Justus von Liebig perform the first confirmed discovery and explanation of isomers, earlier named by Berzelius. Working with cyanic acid and fulminic acid, they correctly deduce that isomerism was caused by differing arrangements of atoms within a molecular structure.[50] 1827

Structural formula of urea

William Prout classifies biomolecules into their modern groupings: carbohydrates, proteins and lipids.[51] 1828 Friedrich Wöhler synthesizes urea, thereby establishing that organic compounds could be produced from inorganic starting materials, disproving the theory of vitalism.[50] 1832 Friedrich Wöhler and Justus von Liebig discover and explain functional groups and radicals in relation to organic chemistry.[50] 1840 Germain Hess proposes Hess's Law, an early statement of the Law of conservation of energy, which establishes that energy changes in a chemical process depend only on the states of the starting and product materials and not on the specific pathway taken between the two states.[52] 1847 Hermann Kolbe obtains acetic acid from completely inorganic sources, further disproving vitalism.[53] 1848 Lord Kelvin establishes concept of absolute zero, the temperature at which all molecular motion ceases.[54] 1849 Louis Pasteur discovers that the racemic form of tartaric acid is a mixture of the levorotatory and dextrotatory forms, thus clarifying the nature of optical rotation and advancing the field of stereochemistry.[55] 1852 August Beer proposes Beer's law, which explains the relationship between the composition of a mixture and the amount of light it will absorb. Based partly on earlier work by Pierre Bouguer and Johann Heinrich Lambert, it establishes the analytical technique known as spectrophotometry.[56] 1855 Benjamin Silliman, Jr. pioneers methods of petroleum cracking, which makes the entire modern petrochemical industry possible.[57] 1856 William Henry Perkin synthesizes Perkin's mauve, the first synthetic dye. Created as an accidental byproduct of an attempt to create quinine from coal tar. This discovery is the foundation of the dye synthesis industry, one of the earliest successful chemical industries.[58] 1857

Timeline of chemistry Friedrich August Kekulé von Stradonitz proposes that carbon is tetravalent, or forms exactly four chemical bonds.[59] 1859–1860 Gustav Kirchhoff and Robert Bunsen lay the foundations of spectroscopy as a means of chemical analysis, which lead them to the discovery of caesium and rubidium. Other workers soon used the same technique to discover indium, thalium, and helium.[60] 1860 Stanislao Cannizzaro, resurrecting Avogadro's ideas regarding diatomic molecules, compiles a table of atomic weights and presents it at the 1860 Karlsruhe Congress, ending decades of conflicting atomic weights and molecular formulas, and leading to Mendeleev's discovery of the periodic law.[61] 1862 Alexander Parkes exhibits Parkesine, one of the earliest synthetic polymers, at the International Exhibition in London. This discovery formed the foundation of the modern plastics industry.[62] 1862 Alexandre-Emile Béguyer de Chancourtois publishes the telluric helix, an early, three-dimensional version of the Periodic Table of the Elements.[63] 1864 John Newlands proposes the law of octaves, a precursor to the Periodic Law.[63] 1864 Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence.[64] 1864 Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet’s ideas, proposed the Law of Mass Action.[65] [66] [67] 1865 Johann Josef Loschmidt determines exact number of molecules in a mole, later named Avogadro's Number.[68] 1865 Friedrich August Kekulé von Stradonitz, based partially on the work of Loschmidt and others, establishes structure of benzene as a six carbon ring with alternating single and double bonds.[59] 1865 Adolf von Baeyer begins work on indigo dye, a milestone in modern industrial organic chemistry which revolutionizes the dye industry.[69]

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1869 Dmitri Mendeleev publishes the first modern periodic table, with the 66 known elements organized by atomic weights. The strength of his table was its ability to accurately predict the properties of as-yet unknown elements.[63] [64] 1873 Jacobus Henricus van 't Hoff and Joseph Achille Le Bel, working independently, develop a model of chemical bonding that explains the chirality experiments of Pasteur and provides a physical cause for optical activity in chiral compounds.[70] 1876 Josiah Willard Gibbs publishes On the Equilibrium of Heterogeneous Substances, a compilation of his work on thermodynamics and physical chemistry which lays out the concept of free energy to explain the physical basis of chemical equilibria.[71]

Mendeleev's 1869 Periodic table

1877 Ludwig Boltzmann establishes statistical derivations of many important physical and chemical concepts, including entropy, and distributions of molecular velocities in the gas phase.[72] 1883 Svante Arrhenius develops ion theory to explain conductivity in electrolytes.[73] 1884 Jacobus Henricus van 't Hoff publishes Études de Dynamique chimique, a seminal study on chemical kinetics.[74] 1884 Hermann Emil Fischer proposes structure of purine, a key structure in many biomolecules, which he later synthesized in 1898. Also begins work on the chemistry of glucose and related sugars.[75] 1884 Henry Louis Le Chatelier develops Le Chatelier's principle, which explains the response of dynamic chemical equilibria to external stresses.[76] 1885 Eugene Goldstein names the cathode ray, later discovered to be composed of electrons, and the canal ray, later discovered to be positive hydrogen ions that had been stripped of their electrons in a cathode ray tube. These would later be named protons.[77] 1893 Alfred Werner discovers the octahedral structure of cobalt complexes, thus establishing the field of coordination chemistry.[78] 1894–1898 William Ramsay discovers the noble gases, which fill a large and unexpected gap in the periodic table and led to models of chemical bonding.[79] 1897 J. J. Thomson discovers the electron using the cathode ray tube.[80]

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1898 Wilhelm Wien demonstrates that canal rays (streams of positive ions) can be deflected by magnetic fields, and that the amount of deflection is proportional to the mass-to-charge ratio. This discovery would lead to the analytical technique known as mass spectrometry.[81] 1898 Maria Sklodowska-Curie and Pierre Curie isolate radium and polonium from pitchblende.[82] c. 1900 Ernest Rutherford discovers the source of radioactivity as decaying atoms; coins terms for various types of radiation.[83]

20th century 1903 Mikhail Semyonovich Tsvet invents chromatography, an important analytic technique.[84] 1904 Hantaro Nagaoka proposes an early nuclear model of the atom, where electrons orbit a dense massive nucleus.[85] 1905 Fritz Haber and Carl Bosch develop the Haber process for making ammonia from its elements, a milestone in industrial chemistry with deep consequences in agriculture.[86] 1905 Albert Einstein explains Brownian motion in a way that definitively proves atomic theory.[87] 1907 Leo Hendrik Baekeland invents bakelite, one of the first commercially successful plastics.[88] 1909 Robert Millikan measures the charge of individual electrons with unprecedented accuracy through the oil drop experiment, confirming that all electrons have the same charge and mass.[89] 1909 S. P. L. Sørensen invents the pH concept and develops methods for measuring acidity.[90] 1911 Antonius Van den Broek proposes the idea that the elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight.[91] 1911

Robert A. Millikan performed the Oil drop experiment.

The first Solvay Conference is held in Brussels, bringing together most of the most prominent scientists of the day. Conferences in physics and chemistry continue to be held periodically to this day.[92] 1911 Ernest Rutherford, Hans Geiger, and Ernest Marsden perform the Gold foil experiment, which proves the nuclear model of the atom, with a small, dense, positive nucleus surrounded by a diffuse electron cloud.[83]

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1912 William Henry Bragg and William Lawrence Bragg propose Bragg's law and establish the field of X-ray crystallography, an important tool for elucidating the crystal structure of substances.[93] 1912 Peter Debye develops the concept of molecular dipole to describe asymmetric charge distribution in some molecules.[94] 1913 Niels Bohr introduces concepts of quantum mechanics to atomic structure by proposing what is now known as the Bohr model of the atom, where electrons exist only in strictly defined orbitals.[95] 1913 Henry Moseley, working from Van den Broek's earlier idea, introduces concept of atomic number to fix inadequacies of Mendeleev's periodic table, which had been based on atomic weight,[96]

The Bohr model of the atom

1913 Frederick Soddy proposes the concept of isotopes, that elements with the same chemical properties may have differing atomic weights.[97] 1913 J. J. Thomson expanding on the work of Wien, shows that charged subatomic particles can be separated by their mass-to-charge ratio, a technique known as mass spectrometry.[98] 1916 Gilbert N. Lewis publishes "The Atom and the Molecule", the foundation of valence bond theory.[99] 1921 Otto Stern and Walther Gerlach establish concept of quantum mechanical spin in subatomic particles.[100] 1923 Gilbert N. Lewis and Merle Randall publish Thermodynamics and the Free Energy of Chemical Substances, first modern treatise on chemical thermodynamics.[101] 1923 Gilbert N. Lewis develops the electron pair theory of acid/base reactions.[99] 1924 Louis de Broglie introduces the wave-model of atomic structure, based on the ideas of wave-particle duality.[102] 1925 Wolfgang Pauli develops the exclusion principle, which states that no two electrons around a single nucleus may have the same quantum state, as described by four quantum numbers.[103]

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1926 Erwin Schrödinger proposes the Schrödinger equation, which provides a mathematical basis for the wave model of atomic structure.[104] 1927

The Schrödinger equation

Werner Heisenberg develops the uncertainty principle which, among other things, explains the mechanics of electron motion around the nucleus.[105] 1927 Fritz London and Walter Heitler apply quantum mechanics to explain covalent bonding in the hydrogen molecule,[106] which marked the birth of quantum chemistry.[107] c. 1930 Linus Pauling proposes Pauling's rules, which are key principles for the use of X-ray crystallography to deduce molecular structure.[108] 1930 Wallace Carothers leads a team of chemists at DuPont who invent nylon, one of the most commercially successful synthetic polymers in history.[109] 1931 Erich Hückel proposes Hückel's rule, which explains when a planar ring molecule will have aromatic properties.[110] Model of two common forms of nylon

1931

Harold Urey discovers deuterium by fractionally distilling liquid hydrogen.[111] 1932 James Chadwick discovers the neutron.[112] 1932–1934 Linus Pauling and Robert Mulliken quantify electronegativity, devising the scales that now bear their names.[113] 1937 Carlo Perrier and Emilio Segrè perform the first confirmed synthesis of technetium-97, the first artificially produced element, filling a gap in the periodic table. Though disputed, the element may have been synthesized as early as 1925 by Walter Noddack and others.[114] 1937 Eugene Houdry develops a method of industrial scale catalytic cracking of petroleum, leading to the development of the first modern oil refinery.[115] 1937 Pyotr Kapitsa, John Allen and Don Misener produce supercooled helium-4, the first zero-viscosity superfluid, a substance that displays quantum mechanical properties on a macroscopic scale.[116] 1938 Otto Hahn discovers the process of nuclear fission in uranium and thorium.[117] 1939

Timeline of chemistry Linus Pauling publishes The Nature of the Chemical Bond, a compilation of a decades worth of work on chemical bonding. It is one of the most important modern chemical texts. It explains hybridization theory, covalent bonding and ionic bonding as explained through electronegativity, and resonance as a means to explain, among other things, the structure of benzene.[108] 1940 Edwin McMillan and Philip H. Abelson identify neptunium, the lightest and first synthesized transuranium element, found in the products of uranium fission. McMillan would found a lab at Berkley that would be involved in the discovery of many new elements and isotopes.[118] 1941 Glenn T. Seaborg takes over McMillan's work creating new atomic nuclei. Pioneers method of neutron capture and later through other nuclear reactions. Would become the principal or co-discoverer of nine new chemical elements, and dozens of new isotopes of existing elements.[118] 1945 Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell perform the first confirmed synthesis of Promethium, filling in the last "gap" in the periodic table.[119] 1945–1946 Felix Bloch and Edward Mills Purcell develop the process of Nuclear Magnetic Resonance, an analytical technique important in elucidating structures of molecules, especially in organic chemistry.[120] 1951 Linus Pauling uses X-ray crystallography to deduce the secondary structure of proteins.[108] 1952 Alan Walsh pioneers the field of atomic absorption spectroscopy, an important quantitative spectroscopy method that allows one to measure specific concentrations of a material in a mixture.[121] 1952 Robert Burns Woodward, Geoffrey Wilkinson, and Ernst Otto Fischer discover the structure of ferrocene, one of the founding discoveries of the field of organometallic chemistry.[122] 1953 James D. Watson and Francis Crick propose the structure of DNA, opening the door to the field of molecular biology.[123] 1957 Jens Skou discovers Na⁺/K⁺-ATPase, the first ion-transporting enzyme.[124] 1958 Max Perutz and John Kendrew use X-ray crystallography to elucidate a protein structure, specifically Sperm Whale myoglobin.[125] 1962 Neil Bartlett synthesizes xenon hexafluoroplatinate, showing for the first time that the noble gases can form chemical compounds.[126] 1962 George Olah observes carbocations via superacid reactions.[127] 1964 Richard R. Ernst performs experiments that will lead to the development of the technique of Fourier Transform NMR. This would greatly increase the sensitivity of the technique, and open the door for magnetic

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resonance imaging or MRI.[128] 1965 Robert Burns Woodward and Roald Hoffmann propose the Woodward-Hoffmann rules, which use the symmetry of molecular orbitals to explain the stereochemistry of chemical reactions.[122] 1966 Hotosi Nozaki and Ryōji Noyori discovered the first example of asymmetric catalysis (hydrogenation) using a structurally well-defined chiral transition metal complex.[129] [130] 1970 John Pople develops the GAUSSIAN program greatly easing computational chemistry calculations.[131] 1971 Yves Chauvin offered an explanation of the reaction mechanism of olefin metathesis reactions.[132] 1975 Karl Barry Sharpless and group discover a stereoselective oxidation reactions including Sharpless epoxidation,[133] [134] Sharpless asymmetric dihydroxylation,[135] [136] [137] and Sharpless oxyamination.[138] [139] [140]

1985 Harold Kroto, Robert Curl and Richard Smalley discover fullerenes, a class of large carbon molecules superficially resembling the geodesic dome designed by architect R. Buckminster Fuller.[141] 1991 Sumio Iijima uses electron microscopy to discover a type of cylindrical fullerene known as a carbon nanotube, though earlier work had been done in the field as early as 1951. This material is an important component in the field of nanotechnology.[142]

Buckminsterfullerene, C60

1994 First total synthesis of Taxol by Robert A. Holton and his group.[143] [144] [145] 1995 Eric Cornell and Carl Wieman produce the first Bose–Einstein condensate, a substance that displays quantum mechanical properties on the macroscopic scale.[146]

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Jensen (2003). "Electronegativity from Avogadro to Pauling: II. Late Nineteenth- and Early Twentieth-Century Developments". Journal of Chemical Education 80 (3): 279. Bibcode 2003JChEd..80..279J. doi:10.1021/ed080p279. [114] "Emilio Segrè: The Nobel Prize in Physics 1959" (http:/ / nobelprize. org/ nobel_prizes/ physics/ laureates/ 1959/ segre-bio. html). Nobel Lectures, Physics 1942–1962. Elsevier Publishing Company. 1965. . Retrieved 2007-02-28. [115] "Eugene Houdry" (http:/ / www. chemheritage. org/ classroom/ chemach/ petroleum/ houdry. html). Chemical Achievers: The Human Face of Chemical Sciences. Chemical Heritage Foundation. 2005. . Retrieved 2007-02-22. [116] "Pyotr Kapitsa: The Nobel Prize in Physics 1978" (http:/ / nobelprize. org/ nobel_prizes/ physics/ laureates/ 1978/ kapitsa-bio. html). Les Prix Nobel, The Nobel Prizes 1991. Nobel Foundation. 1979. . Retrieved 2007-03-26. [117] "Otto Hahn: The Nobel Prize in Chemistry 1944" (http:/ / nobelprize. org/ nobel_prizes/ chemistry/ laureates/ 1944/ hahn-bio. html). Nobel Lectures, Chemistry 1942–1962. Elsevier Publishing Company. 1964. . Retrieved 2007-04-07. [118] "Glenn Theodore Seaborg" (http:/ / www. chemheritage. org/ classroom/ chemach/ atomic/ seaborg. html). Chemical Achievers: The Human Face of Chemical Sciences. Chemical Heritage Foundation. 2005. . Retrieved 2007-02-22. [119] "History of the Elements of the Periodic Table" (http:/ / www. ausetute. com. au/ elemhist. html). AUS-e-TUTE. . Retrieved 2007-03-26. [120] "The Nobel Prize in Physics 1952" (http:/ / nobelprize. org/ nobel_prizes/ physics/ laureates/ 1952/ ). Nobelprize.org. The Nobel Foundation. . Retrieved 2007-02-28. [121] Hannaford, Peter. "Alan Walsh 1916–1998" (http:/ / web. archive. org/ web/ 20070224214248/ http:/ / www. science. org. au/ academy/ memoirs/ walsh2. htm). AAS Biographical Memoirs. Australian Academy of Science. Archived from the original (http:/ / www. science. org. au/ academy/ memoirs/ walsh2. htm) on 2007-02-24. . Retrieved 2007-03-26. [122] Cornforth, Lord Todd, John; Cornforth, J.; T., A. R.; C., J. W. (November 1981). "Robert Burns Woodward. 10 April 1917-8 July 1979". Biographical Memoirs of Fellows of the Royal Society (JSTOR) 27 (Nov., 1981): pp. 628–695. doi:10.1098/rsbm.1981.0025. JSTOR 198111. note: authorization required for web access. [123] "The Nobel Prize in Medicine 1962" (http:/ / nobelprize. org/ nobel_prizes/ medicine/ laureates/ 1962/ ). Nobelprize.org. The Nobel Foundation. . Retrieved 2007-02-28. [124] Skou J (1957). "The influence of some cations on an adenosine triphosphatase from peripheral nerves.". Biochim Biophys Acta 23 (2): 394–401. doi:10.1016/0006-3002(57)90343-8. PMID 13412736. [125] "The Nobel Prize in Chemistry 1962" (http:/ / nobelprize. org/ nobel_prizes/ chemistry/ laureates/ 1962/ ). Nobelprize.org. The Nobel Foundation. . Retrieved 2007-02-28. [126] "Simple experiment" (http:/ / acswebcontent. acs. org/ landmarks/ bartlett/ experiment. html). National historic chemical landmarks. American Chemical Society. . Retrieved 2007-03-02.; Raber, L. Noble Gas Reactivity Research Honored. Chemical and Engineering News, July 3, 2006, Volume 84, Number 27, p. 43 [127] G. A. Olah, S. J. Kuhn, W. S. Tolgyesi, E. B. Baker, J. Am. Chem. Soc. 1962, 84, 2733; G. A. Olah, lieu. Chim. (Buchrest), 1962, 7, 1139 (Nenitzescu issue); G. A. Olah, W. S. Tolgyesi, S. J. Kuhn, M. E. Moffatt, I. J. Bastien, E. B. Baker, J. Am. Chem. Soc. 1963, 85, 1328. [128] "Richard R. Ernst The Nobel Prize in Chemistry 1991" (http:/ / nobelprize. org/ nobel_prizes/ chemistry/ laureates/ 1991/ ernst-autobio. html). Les Prix Nobel, The Nobel Prizes 1991. Nobel Foundation. 1992. . Retrieved 2007-03-27.

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Timeline of chemistry [129] H. Nozaki, S. Moriuti, H. Takaya, R. Noyori, Tetrahedron Lett. 1966, 5239; [130] H. Nozaki, H. Takaya, S. Moriuti, R. Noyori, Tetrahedron 1968, 24, 3655. [131] W. J. Hehre, W. A. Lathan, R. Ditchfield, M. D. Newton, and J. A. Pople, Gaussian 70 (Quantum Chemistry Program Exchange, Program No. 237, 1970). [132] Catalyse de transformation des oléfines par les complexes du tungstène. II. Télomérisation des oléfines cycliques en présence d'oléfines acycliques Die Makromolekulare Chemie Volume 141, Issue 1, Date: 9 February 1971, Pages: 161–176 Par Jean-Louis Hérisson, Yves Chauvin doi:10.1002/macp.1971.021410112 [133] Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 5974. (doi:10.1021/ja00538a077) [134] Hill, J. G.; Sharpless, K. B.; Exon, C. M.; Regenye, R. Org. Syn., Coll. Vol. 7, p.461 (1990); Vol. 63, p.66 (1985). ( Article (http:/ / www. orgsyn. org/ orgsyn/ prep. asp?prep=cv7p0461)) [135] Jacobsen, E. N.; Marko, I.; Mungall, W. S.; Schroeder, G.; Sharpless, K. B. J. Am. Chem. Soc. 1988, 110, 1968. (doi:10.1021/ja00214a053) [136] Kolb, H. C.; Van Nieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94, 2483–2547. (Review) (doi:10.1021/cr00032a009) [137] Gonzalez, J.; Aurigemma, C.; Truesdale, L. Org. Syn., Coll. Vol. 10, p.603 (2004); Vol. 79, p.93 (2002). ( Article (http:/ / www. orgsyn. org/ orgsyn/ prep. asp?prep=v79p0093)) [138] Sharpless, K. B.; Patrick, D. W.; Truesdale, L. K.; Biller, S. A. J. Am. Chem. Soc. 1975, 97, 2305. (doi:10.1021/ja00841a071) [139] Herranz, E.; Biller, S. A.; Sharpless, K. B. J. Am. Chem. Soc. 1978, 100, 3596–3598. (doi:10.1021/ja00479a051) [140] Herranz, E.; Sharpless, K. B. Org. Syn., Coll. Vol. 7, p.375 (1990); Vol. 61, p.85 (1983). ( Article (http:/ / www. orgsyn. org/ orgsyn/ prep. asp?prep=cv7p0375)) [141] "The Nobel Prize in Chemistry 1996" (http:/ / nobelprize. org/ nobel_prizes/ chemistry/ laureates/ 1996/ ). Nobelprize.org. The Nobel Foundation. . Retrieved 2007-02-28. [142] "Benjamin Franklin Medal awarded to Dr. Sumio Iijima, Director of the Research Center for Advanced Carbon Materials, AIST" (http:/ / www. aist. go. jp/ aist_e/ topics/ 20020129/ 20020129. html). National Institute of Advanced Industrial Science and Technology. 2002. . Retrieved 2007-03-27. [143] First total synthesis of taxol 1. Functionalization of the B ring Robert A. Holton, Carmen Somoza, Hyeong Baik Kim, Feng Liang, Ronald J. Biediger, P. Douglas Boatman, Mitsuru Shindo, Chase C. Smith, Soekchan Kim, et al.; J. Am. Chem. Soc.; 1994; 116(4); 1597–1598. DOI Abstract (http:/ / pubs. acs. org/ doi/ abs/ 10. 1021/ ja00083a066) [144] First total synthesis of taxol. 2. Completion of the C and D rings Robert A. Holton, Hyeong Baik Kim, Carmen Somoza, Feng Liang, Ronald J. Biediger, P. Douglas Boatman, Mitsuru Shindo, Chase C. Smith, Soekchan Kim, and et al. J. Am. Chem. Soc.; 1994; 116(4) pp 1599–1600 DOI Abstract (http:/ / pubs. acs. org/ doi/ abs/ 10. 1021/ ja00083a067) [145] A synthesis of taxusin Robert A. Holton, R. R. Juo, Hyeong B. Kim, Andrew D. Williams, Shinya Harusawa, Richard E. Lowenthal, Sadamu Yogai J. Am. Chem. Soc.; 1988; 110(19); 6558–6560. Abstract (http:/ / pubs. acs. org/ doi/ abs/ 10. 1021/ ja00227a043) [146] "Cornell and Wieman Share 2001 Nobel Prize in Physics" (http:/ / www. nist. gov/ public_affairs/ releases/ n01-04. htm). NIST News Release. National Institute of Standards and Technology. 2001. . Retrieved 2007-03-27.

Further reading • Servos, John W., Physical chemistry from Ostwald to Pauling : the making of a science in America (http://books. google.com/books?id=1UZjU2WfLAoC&printsec=frontcover), Princeton, N.J. : Princeton University Press, 1990. ISBN 0691085668

External links • Chemical Achievers: The Human Face of the Chemical Sciences (http://www.chemheritage.org/classroom/ chemach/index.html) • Eric Weisstein's World of Scientific Biography (http://scienceworld.wolfram.com/biography/) • History of Gas Chemistry (http://mattson.creighton.edu/HistoryGasChemistry.html) • list of all Nobel Prize laureates (http://nobelprize.org/nobel_prizes/lists/all/) • History of Elements of the Periodic Table (http://www.ausetute.com.au/elemhist.html) • Chemsoc timeline (http://www.chemsoc.org/timeline/pages/timeline.html)

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Atoms and molecules Atom Helium atom

An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is one angstrom ( × 10−10 m or 100 pm). Classification

Smallest recognized division of a chemical element

Properties

Mass range:

1.67 × 10−27 to 4.52 × 10−25 kg

Electric charge: zero (neutral), or ion charge Diameter range: 62 pm (He) to 520 pm (Cs) (data page) Components:

Electrons and a compact nucleus of protons and neutrons

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive charge if there are fewer electrons (electron deficiency) or negative charge if there are more electrons (electron excess). A positively or negatively charged atom is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.[1]

Atom The name atom comes from the Greek ἄτομος (atomos, “indivisible”) from ἀ- (a-, “not”) and τέμνω (temnō, “I cut”)[2] , which means uncuttable, or indivisible, something that cannot be divided further.[3] The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.[4] [5] Atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.94% of an atom's mass is concentrated in the nucleus,[6] with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus.[7] Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.

History Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny quantities has been around for millennia, but these ideas were founded in abstract, philosophical reasoning rather than experimentation and empirical observation. The nature of atoms in philosophy varied considerably over time and between cultures and schools, and often had spiritual elements. Nevertheless, the basic idea of the atom was adopted by scientists thousands of years later because it elegantly explained new discoveries in the field of chemistry.[8] References to the concept of atoms date back to ancient Greece and India. In India, the Ājīvika, Jain, and Cārvāka schools of atomism may date back to the 6th century BCE.[9] The Nyaya and Vaisheshika schools later developed theories on how atoms combined into more complex objects.[10] In the West, the references to atoms emerged in the 5th century BCE with Leucippus, whose student, Democritus, systematized his views. In approximately 450 BCE, Democritus coined the term átomos (Greek: ἄτομος), which means "uncuttable" or "the smallest indivisible particle of matter". Although the Indian and Greek concepts of the atom were based purely on philosophy, modern science has retained the name coined by Democritus.[8] Corpuscularianism is the postulate, expounded in the 13th-century by the alchemist Pseudo-Geber (Geber),[11] sometimes identified with Paul of Taranto, that all physical bodies possess an inner and outer layer of minute particles or corpuscles.[12] Corpuscularianism is similar (this is the electrical pulses ) to the theory atomism, except that where atoms were supposed to be indivisible, corpuscles could in principle be divided. In this manner, for example, it was theorized that mercury could penetrate into metals and modify their inner structure.[13] Corpuscularianism stayed a dominant theory over the next several hundred years. In 1661, natural philosopher Robert Boyle published The Sceptical Chymist in which he argued that matter was composed of various combinations of different "corpuscules" or atoms, rather than the classical elements of air, earth, fire and water.[14] During the 1670s corpuscularianism was used by Isaac Newton in his development of the corpuscular theory of light.[12] [15]

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67

Origin of scientific theory Further progress in the understanding of atoms did not occur until the science of chemistry began to develop. In 1789, French nobleman and scientific researcher Antoine Lavoisier discovered the law of conservation of mass and defined an element as a basic substance that could not be further broken down by the methods of chemistry.[16] In 1805, English instructor and natural philosopher John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers (the law of multiple proportions) and why certain gases dissolved better in water than others. He proposed that each element consists of atoms of a single, unique type, and that these atoms can join together to form chemical compounds.[17] [18] Dalton is considered the originator of modern atomic theory.[19]

Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808), one of the earliest scientific works on atomic theory.

Dalton's atomic hypothesis did not specify the size of atoms. Common sense indicated they must be very small, but nobody knew how small. Therefore it was a major landmark when in 1865 Johann Josef Loschmidt measured the size of the molecules that make up air. An additional line of reasoning in support of particle theory (and by extension atomic theory) began in 1827 when botanist Robert Brown used a microscope to look at dust grains floating in water and discovered that they moved about erratically—a phenomenon that became known as "Brownian motion". J. Desaulx suggested in 1877 that the phenomenon was caused by the thermal motion of water molecules, and in 1905 Albert Einstein produced the first mathematical analysis of the motion.[20] [21] [22] French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of atoms, thereby conclusively verifying Dalton's atomic theory.[23] In 1869, building upon earlier discoveries by such scientists as Lavoisier, Dmitri Mendeleev published the first functional periodic table.[24] The table itself is a visual representation of the periodic law, which states that certain chemical properties of elements repeat periodically when arranged by atomic number.[25]

Subcomponents and quantum theory

Mendeleev's first periodic table (1869).

The physicist J. J. Thomson, through his work on cathode rays in 1897, discovered the electron, and concluded that they were a component of every atom. Thus he overturned the belief that atoms are the indivisible, ultimate particles of matter.[26] Thomson postulated that the low mass, negatively charged electrons were distributed throughout the atom, possibly rotating in rings, with their charge balanced by the presence of a uniform sea of positive charge. This later became known as the plum pudding model.

In 1909, Hans Geiger and Ernest Marsden, under the direction of physicist Ernest Rutherford, bombarded a sheet of gold foil with alpha rays—by then known to be positively charged helium atoms—and discovered that a small percentage of these particles were deflected through much larger angles than was predicted using Thomson's proposal. Rutherford interpreted the gold foil experiment as suggesting that the positive charge of a heavy gold atom and most of its mass was concentrated in a nucleus at the center of the atom—the Rutherford model.[27]

Atom While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table.[28] The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J.J. Thomson created a technique for separating atom types through his work on ionized gases, which subsequently led to the discovery of stable isotopes.[29] Meanwhile, in 1913, physicist Niels Bohr suggested that the electrons were confined into clearly defined, quantized orbits, and could jump between these, but could not freely spiral inward or outward in intermediate states.[30] An electron must absorb or emit specific amounts of energy to transition between these fixed orbits. When the light from a heated material was passed through a prism, it produced a multi-colored spectrum. The appearance of fixed lines in this spectrum was successfully explained by these orbital transitions.[31] Later in the same year Henry Moseley provided additional experimental evidence in favor of Niels Bohr's theory. These results A Bohr model of the hydrogen atom, showing an refined Ernest Rutherford's and Antonius Van den Broek's model, electron jumping between fixed orbits and emitting a photon of energy with a specific which proposed that the atom contains in its nucleus a number of frequency. positive nuclear charges that is equal to its (atomic) number in the periodic table. Until these experiments, atomic number was not known to be a physical and experimental quantity. That it is equal to the atomic nuclear charge remains the accepted atomic model today.[32] Chemical bonds between atoms were now explained, by Gilbert Newton Lewis in 1916, as the interactions between their constituent electrons.[33] As the chemical properties of the elements were known to largely repeat themselves according to the periodic law,[34] in 1919 the American chemist Irving Langmuir suggested that this could be explained if the electrons in an atom were connected or clustered in some manner. Groups of electrons were thought to occupy a set of electron shells about the nucleus.[35] The Stern–Gerlach experiment of 1922 provided further evidence of the quantum nature of the atom. When a beam of silver atoms was passed through a specially shaped magnetic field, the beam was split based on the direction of an atom's angular momentum, or spin. As this direction is random, the beam could be expected to spread into a line. Instead, the beam was split into two parts, depending on whether the atomic spin was oriented up or down.[36] In 1924, Louis de Broglie proposed that all particles behave to an extent like waves. In 1926, Erwin Schrödinger used this idea to develop a mathematical model of the atom that described the electrons as three-dimensional waveforms rather than point particles. A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at the same time; this became known as the uncertainty principle, formulated by Werner Heisenberg in 1926. In this concept, for a given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa. This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed.[37] [38]

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Atom

69 The development of the mass spectrometer allowed the exact mass of atoms to be measured. The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge. The chemist Francis William Aston used this instrument to show that isotopes had different masses. The atomic mass of these isotopes varied by integer amounts, called the whole number rule.[39] The explanation for these different isotopes awaited the discovery of the neutron, a neutral-charged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus.[40] Schematic diagram of a simple mass spectrometer.

Fission, high energy physics and condensed matter In 1938, the German chemist Otto Hahn, a student of Rutherford, directed neutrons onto uranium atoms expecting to get transuranium elements. Instead, his chemical experiments showed barium as a product.[41] A year later, Lise Meitner and her nephew Otto Frisch verified that Hahn's result were the first experimental nuclear fission.[42] [43] In 1944, Hahn received the Nobel prize in chemistry. Despite Hahn's efforts, the contributions of Meitner and Frisch were not recognized.[44] In the 1950s, the development of improved particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies.[45] Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. Standard models of nuclear physics were developed that successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions.[46]

Components Subatomic particles Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron. However, the hydrogen-1 atom has no neutrons and a positive hydrogen ion has no electrons. The electron is by far the least massive of these particles at 9.11 × 10−31 kg, with a negative electrical charge and a size that is too small to be measured using available techniques.[47] Protons have a positive charge and a mass 1,836 times that of the electron, at 1.6726 × 10−27 kg, although this can be reduced by changes to the energy binding the proton into an atom. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of electrons,[48] or 1.6929 × 10−27 kg. Neutrons and protons have comparable dimensions—on the order of 2.5 × 10−15 m—although the 'surface' of these particles is not sharply defined.[49] In the Standard Model of physics, both protons and neutrons are composed of elementary particles called quarks. The quark belongs to the fermion group of particles, and is one of the two basic constituents of matter—the other being the lepton, of which the electron is an example. There are six types of quarks, each having a fractional electric charge of either +2⁄3 or −1⁄3. Protons are composed of two up quarks and one down quark, while a neutron consists of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles. The quarks are held together by the strong nuclear force, which is mediated by gluons. The gluon is a member of the family of gauge bosons, which are elementary particles that mediate physical forces.[50] [51]

Atom

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Nucleus

The binding energy needed for a nucleon to escape the nucleus, for various isotopes.

All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to , where A is the total number of nucleons.[52] This is much smaller than the radius of the atom, which is on the order of 105 fm. The nucleons are bound together by a short-ranged attractive potential called the residual strong force. At distances smaller than 2.5 fm this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other.[53] Atoms of the same element have the same number of protons, called the atomic number. Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay.[54] The neutron and the proton are different types of fermions. The Pauli exclusion principle is a quantum mechanical effect that prohibits identical fermions, such as multiple protons, from occupying the same quantum physical state at the same time. Thus every proton in the nucleus must occupy a different state, with its own energy level, and the same rule applies to all of the neutrons. This prohibition does not apply to a proton and neutron occupying the same quantum state.[55] For atoms with low atomic numbers, a nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with roughly matching numbers of protons and neutrons are more stable against decay. However, with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus, which modifies this trend. Thus, there are no stable nuclei with equal proton and neutron numbers above atomic number Z = 20 (calcium); and as Z increases toward the heaviest nuclei, the ratio of neutrons per proton required for stability increases to about 1.5.[55]

Atom

The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3–10 keV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus.[56] Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element.[57] [58] If the mass of the nucleus following a fusion reaction is less than the Illustration of a nuclear fusion process that forms sum of the masses of the separate particles, then the difference between a deuterium nucleus, consisting of a proton and a these two values can be emitted as a type of usable energy (such as a neutron, from two protons. A positron (e+)—an antimatter electron—is emitted along with an gamma ray, or the kinetic energy of a beta particle), as described by 2 electron neutrino. Albert Einstein's mass–energy equivalence formula, E = mc , where m is the mass loss and c is the speed of light. This deficit is part of the binding energy of the new nucleus, and it is the non-recoverable loss of the energy that causes the fused particles to remain together in a state that requires this energy to separate.[59] The fusion of two nuclei that create larger nuclei with lower atomic numbers than iron and nickel—a total nucleon number of about 60—is usually an exothermic process that releases more energy than is required to bring them together.[60] It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decrease. That means fusion processes producing nuclei that have atomic numbers higher than about 26, and atomic masses higher than about 60, is an endothermic process. These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star.[55]

Electron cloud The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at greater separations. Electrons, like other particles, have properties of both a particle and a A potential well, showing, according to classical wave. The electron cloud is a region inside the potential well where mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with each electron forms a type of three-dimensional standing wave—a energy E is constrained to a range of positions wave form that does not move relative to the nucleus. This behavior is between x1 and x2. defined by an atomic orbital, a mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured.[61] Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form.[62] Orbitals can have one or more ring or node structures, and they differ from each other in size, shape and orientation.[63]

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72

Wave functions of the first five atomic orbitals. The three 2p orbitals each display a single angular node that has an orientation and a minimum at the center.

Each atomic orbital corresponds to a particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines.[62]

The amount of energy needed to remove or add an electron—the electron binding energy—is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom,[64] compared to 2.23 million eV for splitting a deuterium nucleus.[65] Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals.[66]

Properties Nuclear properties By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form,[67] also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element hydrogen up to the 118-proton element ununoctium.[68] All known isotopes of elements with atomic numbers greater than 82 are radioactive.[69] [70] About 339 nuclides occur naturally on Earth,[71] of which 255 (about 75%) have not been observed to decay, and are referred to as "stable isotopes". However, only 90 of these nuclides are stable to all decay, even in theory. Another 165 (bringing the total to 255) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 33 radioactive nuclides have half-lives longer than 80 million years, and are long-lived enough to be present from the birth of the solar system. This collection of 288 nuclides are known as primordial nuclides. Finally, an additional 51 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or else as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14).[72] [73] For 80 of the chemical elements, at least one stable isotope exists. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes. As a rule, there is, for each element, only a handful of stable isotopes, the average being 3.2 stable isotopes per element among those that have stable isotopes. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin.[74] Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 255 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10 and nitrogen-14. Also, only four naturally occurring, radioactive odd-odd nuclides have a half-life over a billion years: potassium-40, vanadium-50, lanthanum-138 and tantalum-180m. Most odd-odd nuclei are highly unstable with respect to beta decay, because the

Atom decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects.[74]

Mass The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. The mass number is a simple whole number, and has units of "nucleons." An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). The actual mass of an atom at rest is often expressed using the unified atomic mass unit (u), which is also called a dalton (Da). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 1.66 × 10−27 kg.[75] Hydrogen-1, the lightest isotope of hydrogen and the atom with the lowest mass, has an atomic weight of 1.007825 u.[76] The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the mass of the atomic mass unit. However, this number will not be an exact whole number except in the case of carbon-12 (see below)[77] The heaviest stable atom is lead-208,[69] with a mass of 207.9766521 u.[78] As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. The mole is defined such that one mole of any element always has the same number of atoms (about 6.022 × 1023). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 u, and so a mole of carbon-12 atoms weighs exactly 0.012 kg.[75]

Shape and size Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin.[79] On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right).[80] Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm.[81] When subjected to external fields, like an electrical field, the shape of an atom may deviate from that of a sphere. The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals, where large crystal-electrical fields may occur at low-symmetry lattice sites.[82] Significant ellipsoidal deformations have recently been shown to occur for sulfur ions in pyrite-type compounds.[83] Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they can not be viewed using an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width.[84] A single drop of water contains about 2 sextillion (2 × 1021) atoms of oxygen, and twice the number of hydrogen atoms.[85] A single carat diamond with a mass of 2 × 10−4 kg contains about 10 sextillion (1022) atoms of carbon.[86] If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.[87]

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Radioactive decay Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm.[88] The most common forms of radioactive decay are:[89] [90] • Alpha decay is caused when the nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. The result of the emission is a new element with a lower atomic number. • Beta decay is regulated by the weak force, and results from a transformation of a neutron into a proton, or a proton into a neutron. The first is accompanied by the emission of an electron and an antineutrino, while the second causes the This diagram shows the half-life (T½) of various isotopes with Z protons and N emission of a positron and a neutrino. neutrons. The electron or positron emissions are called beta particles. Beta decay either increases or decreases the atomic number of the nucleus by one. • Gamma decay results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. This can occur following the emission of an alpha or a beta particle from radioactive decay. Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle, or result (through internal conversion) in production of high-speed electrons that are not beta rays, and high-energy photons that are not gamma rays. Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth.[88]

Magnetic moment Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is measured in units of the reduced Planck constant (ħ), with electrons, protons and neutrons all having spin ½ ħ, or "spin-½". In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin.[91]

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Atom The magnetic field produced by an atom—its magnetic moment—is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field. However, the most dominant contribution comes from spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons.[92] In ferromagnetic elements such as iron, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field.[92] [93] The nucleus of an atom can also have a net spin. Normally these nuclei are aligned in random directions because of thermal equilibrium. However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging.[94] [95]

Energy levels When an electron is bound to an atom, it has a potential energy that is inversely proportional to its distance from the nucleus. This is measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). In the quantum mechanical model, a bound electron can only occupy a set of states centered on the nucleus, and each state corresponds to a specific energy level. The lowest energy state of a bound electron is called the ground state, while an electron at a higher energy level is in an excited state.[96] For an electron to transition between two different states, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels. The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum.[97] Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors.[98] When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom spontaneously emit this energy as a An example of absorption lines in a spectrum. photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. (An observer viewing the atoms from a view that does not include the continuous spectrum in the background, instead sees a series of emission lines from the photons emitted by the atoms.) Spectroscopic measurements of the strength and width of spectral lines allow the composition and physical properties of a substance to be determined.[99] Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin-orbit coupling, which is an interaction between the spin and motion of the outermost electron.[100] When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron

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configurations to slightly different energy levels, resulting in multiple spectral lines.[101] The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect.[102] If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon then move off in parallel and with matching phases. That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band.[103]

Valence and bonding behavior The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. The number of valence electrons determines the bonding behavior with other atoms. Atoms tend to chemically react with each other in a manner that fills (or empties) their outer valence shells.[104] For example, a transfer of a single electron between atoms is a useful approximation for bonds that form between atoms with one-electron more than a filled shell, and others that are one-electron short of a full shell, such as occurs in the compound sodium chloride and other chemical ionic salts. However, many elements display multiple valences, or tendencies to share differing numbers of electrons in different compounds. Thus, chemical bonding between these elements takes many forms of electron-sharing that are more than simple electron transfers. Examples include the element carbon and the organic compounds.[105] The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases.[106] [107]

States Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases and plasmas. [108] Within a state, a material can also exist in different phases. An example of this is solid carbon, which can exist as graphite or diamond.[109] At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects, Snapshots illustrating the formation of a which are normally only observed at the atomic scale, become apparent Bose–Einstein condensate. on a macroscopic scale.[110] [111] This super-cooled collection of atoms then behaves as a single super atom, which may allow fundamental checks of quantum mechanical behavior.[112]

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Identification The scanning tunneling microscope is a device for viewing surfaces at the atomic level. It uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would normally be insurmountable. Electrons tunnel through the vacuum between two planar metal electrodes, on each of which is an adsorbed atom, providing a tunneling-current density that can be measured. Scanning one atom (taken as the tip) as it moves past the other (the sample) permits plotting of tip displacement versus lateral separation for a constant current. The calculation shows the extent to which scanning-tunneling-microscope images of an individual atom are visible. It confirms that for low bias, the microscope images the space-averaged dimensions of the electron orbitals across closely packed energy levels—the Fermi level local density of states.[113] [114]

Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface. Reconstruction causes the surface atoms to deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them.

An atom can be ionized by removing one of its electrons. The electric charge causes the trajectory of an atom to bend when it passes through a magnetic field. The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis.[115] A more area-selective method is electron energy loss spectroscopy, which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample. The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry.[116] Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. These colors can be replicated using a gas-discharge lamp containing the same element.[117] Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth.[118]

Origin and current state Atoms form about 4% of the total energy density of the observable universe, with an average density of about 0.25 atoms/m3.[119] Within a galaxy such as the Milky Way, atoms have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3.[120] The Sun is believed to be inside the Local Bubble, a region of highly ionized gas, so the density in the solar neighborhood is only about 103 atoms/m3.[121] Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium. Up to 95% of the Milky Way's atoms are concentrated inside stars and the total mass of atoms forms about 10% of the mass of the galaxy.[122] (The remainder of the mass is an unknown dark matter.)[123]

Atom

Nucleosynthesis Stable protons and electrons appeared one second after the Big Bang. During the following three minutes, Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the universe, and perhaps some of the beryllium and boron.[124] [125] [126] The first atoms (complete with bound electrons) were theoretically created 380,000 years after the Big Bang—an epoch called recombination, when the expanding universe cooled enough to allow electrons to become attached to nuclei.[127] Since the Big Bang, which produced no carbon, atomic nuclei have been combined in stars through the process of nuclear fusion to produce more of the element helium, and (via the triple alpha process) the sequence of elements from carbon up to iron.[128] Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation.[129] This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected. Elements heavier than iron were produced in supernovae through the r-process and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei.[130] Elements such as lead formed largely through the radioactive decay of heavier elements.[131]

Earth Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating.[132] [133] Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay.[134] There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere.[135] Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions.[136] [137] Of the transuranic elements—those with atomic numbers greater than 92—only plutonium and neptunium occur naturally on Earth.[138] [139] Transuranic elements have radioactive lifetimes shorter than the current age of the Earth[140] and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust.[132] Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore.[141] The Earth contains approximately 1.33 × 1050 atoms.[142] In the planet's atmosphere, small numbers of independent atoms of noble gases exist, such as argon and neon. The remaining 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. At the surface of the Earth, atoms combine to form various compounds, including water, salt, silicates and oxides. Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals.[143] [144] This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter.[145]

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Rare and theoretical forms While isotopes with atomic numbers higher than lead (82) are known to be radioactive, an "island of stability" has been proposed for some elements with atomic numbers above 103. These superheavy elements may have a nucleus that is relatively stable against radioactive decay.[146] The most likely candidate for a stable superheavy atom, unbihexium, has 126 protons and 184 neutrons.[147] Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each other. Because of this, along with an imbalance between the number of matter and antimatter particles, the latter are rare in the universe. (The first causes of this imbalance are not yet fully understood, although the baryogenesis theories may offer an explanation.) As a result, no antimatter atoms have been discovered in nature.[148] [149] However, in 1996, antihydrogen, the antimatter counterpart of hydrogen, was synthesized at the CERN laboratory in Geneva.[150] [151] Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. For example, an electron can be replaced by a more massive muon, forming a muonic atom. These types of atoms can be used to test the fundamental predictions of physics.[152] [153] [154]

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, or 99.95% of the total atomic mass. All other

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References Book references • L'Annunziata, Michael F. (2003). Handbook of Radioactivity Analysis. Academic Press. ISBN 0-12-436603-1. OCLC 16212955. • Beyer, H. F.; Shevelko, V. P. (2003). Introduction to the Physics of Highly Charged Ions. CRC Press. ISBN 0-7503-0481-2. OCLC 47150433. • Choppin, Gregory R.; Liljenzin, Jan-Olov; Rydberg, Jan (2001). Radiochemistry and Nuclear Chemistry. Elsevier. ISBN 0-7506-7463-6. OCLC 162592180. • Dalton, J. (1808). A New System of Chemical Philosophy, Part 1. London and Manchester: S. Russell. • Demtröder, Wolfgang (2002). Atoms, Molecules and Photons: An Introduction to Atomic- Molecular- and Quantum Physics (1st ed.). Springer. ISBN 3-540-20631-0. OCLC 181435713. • Feynman, Richard (1995). Six Easy Pieces. The Penguin Group. ISBN 978-0-14-027666-4. OCLC 40499574. • Fowles, Grant R. (1989). Introduction to Modern Optics. Courier Dover Publications. ISBN 0-486-65957-7. OCLC 18834711. • Gangopadhyaya, Mrinalkanti (1981). Indian Atomism: History and Sources. Atlantic Highlands, New Jersey: Humanities Press. ISBN 0-391-02177-X. OCLC 10916778. • Goodstein, David L. (2002). States of Matter. Courier Dover Publications. ISBN 0-13-843557-X. • Harrison, Edward Robert (2003). Masks of the Universe: Changing Ideas on the Nature of the Cosmos. Cambridge University Press. ISBN 0-521-77351-2. OCLC 50441595. • Iannone, A. Pablo (2001). Dictionary of World Philosophy. Routledge. ISBN 0-415-17995-5. OCLC 44541769. • Jevremovic, Tatjana (2005). Nuclear Principles in Engineering. Springer. ISBN 0-387-23284-2. OCLC 228384008. • King, Richard (1999). Indian philosophy: an introduction to Hindu and Buddhist thought. Edinburgh University Press. ISBN 0-7486-0954-7. • Lequeux, James (2005). The Interstellar Medium. Springer. ISBN 3-540-21326-0. OCLC 133157789. • Levere, Trevor, H. (2001). Transforming Matter – A History of Chemistry for Alchemy to the Buckyball. The Johns Hopkins University Press. ISBN 0-8018-6610-3. • Liang, Z.-P.; Haacke, E. M. (1999). Webster, J. G.. ed (PDF). Encyclopedia of Electrical and Electronics Engineering: Magnetic Resonance Imaging (http://ieeexplore.ieee.org/iel5/8734/27658/01233976. pdf?arnumber=1233976). vol. 2. John Wiley & Sons. pp. 412–26. ISBN 0-471-13946-7. Retrieved 2008-01-09. • McEvilley, Thomas (2002). The shape of ancient thought: comparative studies in Greek and Indian philosophies. Allworth Press. ISBN 1-58115-203-5. • MacGregor, Malcolm H. (1992). The Enigmatic Electron. Oxford University Press. ISBN 0-19-521833-7. OCLC 223372888. • Manuel, Oliver (2001). Origin of Elements in the Solar System: Implications of Post-1957 Observations. Springer. ISBN 0-306-46562-0. OCLC 228374906. • Mazo, Robert M. (2002). Brownian Motion: Fluctuations, Dynamics, and Applications. Oxford University Press. ISBN 0-19-851567-7. OCLC 48753074.

Atom • Mills, Ian; Cvitaš, Tomislav; Homann, Klaus; Kallay, Nikola; Kuchitsu, Kozo (1993). Quantities, Units and Symbols in Physical Chemistry (2nd ed.). Oxford: International Union of Pure and Applied Chemistry, Commission on Physiochemical Symbols Terminology and Units, Blackwell Scientific Publications. ISBN 0-632-03583-8. OCLC 27011505. • Moran, Bruce T. (2005). Distilling Knowledge: Alchemy, Chemistry, and the Scientific Revolution. Harvard University Press. ISBN 0-674-01495-2. • Myers, Richard (2003). The Basics of Chemistry. Greenwood Press. ISBN 0-313-31664-3. OCLC 50164580. • Padilla, Michael J.; Miaoulis, Ioannis; Cyr, Martha (2002). Prentice Hall Science Explorer: Chemical Building Blocks. Upper Saddle River, New Jersey USA: Prentice-Hall, Inc.. ISBN 0-13-054091-9. OCLC 47925884. • Pais, Abraham (1986). Inward Bound: Of Matter and Forces in the Physical World. New York: Oxford University Press. ISBN 0198519710. • Pauling, Linus (1960). The Nature of the Chemical Bond. Cornell University Press. ISBN 0-8014-0333-2. OCLC 17518275. • Pfeffer, Jeremy I.; Nir, Shlomo (2000). Modern Physics: An Introductory Text. Imperial College Press. ISBN 1-86094-250-4. OCLC 45900880. • Ponomarev, Leonid Ivanovich (1993). The Quantum Dice. CRC Press. ISBN 0-7503-0251-8. OCLC 26853108. • Roscoe, Henry Enfield (1895). John Dalton and the Rise of Modern Chemistry (http://books.google.com/ books?id=FJMEAAAAYAAJ). Century science series. New York: Macmillan. Retrieved 2011-04-03. • Scerri, Eric R. (2007). The periodic table: its story and its significance. Oxford University Press US. ISBN 0-19-530573-6. • Shultis, J. Kenneth; Faw, Richard E. (2002). Fundamentals of Nuclear Science and Engineering. CRC Press. ISBN 0-8247-0834-2. OCLC 123346507. • Siegfried, Robert (2002). From Elements to Atoms: A History of Chemical Composition. DIANE. ISBN 0-87169-924-9. OCLC 186607849. • Sills, Alan D. (2003). Earth Science the Easy Way. Barron's Educational Series. ISBN 0-7641-2146-4. OCLC 51543743. • Smirnov, Boris M. (2003). Physics of Atoms and Ions. Springer. ISBN 0-387-95550-X. • Teresi, Dick (2003). Lost Discoveries: The Ancient Roots of Modern Science (http://books.google.com/ ?id=pheL_ubbXD0C&dq). Simon & Schuster. pp. 213–214. ISBN 0-7432-4379-X. • Various (2002). Lide, David R.. ed. Handbook of Chemistry & Physics (http://www.hbcpnetbase.com/) (88th ed.). CRC. ISBN 0-8493-0486-5. OCLC 179976746. Retrieved 2008-05-23. • Woan, Graham (2000). The Cambridge Handbook of Physics. Cambridge University Press. ISBN 0-521-57507-9. OCLC 224032426. • Wurtz, Charles Adolphe (1881). The Atomic Theory. New York: D. Appleton and company. ISBN 0-559-43636-X. • Zaider, Marco; Rossi, Harald H. (2001). Radiation Science for Physicians and Public Health Workers. Springer. ISBN 0-306-46403-9. OCLC 44110319. • Zumdahl, Steven S. (2002). Introductory Chemistry: A Foundation (http://college.hmco.com/chemistry/intro/ zumdahl/intro_chemistry/5e/students/protected/periodictables/pt/pt/pt_ar5.html) (5th ed.). Houghton Mifflin. ISBN 0-618-34342-3. OCLC 173081482. Retrieved 2008-02-05.

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External links • Francis, Eden (2002). "Atomic Size" (http://dl.clackamas.cc.or.us/ch104-07/atomic_size.htm). Clackamas Community College. Retrieved 2007-01-09. • Freudenrich, Craig C.. "How Atoms Work" (http://www.howstuffworks.com/atom.htm). How Stuff Works. Retrieved 2007-01-09. • "The Atom" (http://en.wikibooks.org/wiki/FHSST_Physics/Atom). Free High School Science Texts: Physics. Wikibooks. Retrieved 2010-07-10. • Anonymous (2007). "The atom" (http://www.scienceaid.co.uk/chemistry/fundamental/atom.html). Science aid+. Retrieved 2010-07-10.—a guide to the atom for teens. • Anonymous (2006-01-03). "Atoms and Atomic Structure" (http://www.bbc.co.uk/dna/h2g2/A6672963). BBC. Retrieved 2007-01-11. • Various (2006-01-03). "Physics 2000, Table of Contents" (http://www.colorado.edu/physics/2000/index. pl?Type=TOC). University of Colorado. Retrieved 2008-01-11. • Various (2006-02-03). "What does an atom look like?" (http://www.hydrogenlab.de/elektronium/HTML/ einleitung_hauptseite_uk.html). University of Karlsruhe. Retrieved 2008-05-12.

Atomic nucleus

86

Atomic nucleus

87

The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The proton–neutron model of nucleus was proposed by Dmitry Ivanenko in 1932. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the orbiting electrons. The diameter of the nucleus is in the range of 1.75 fm (femtometre) (1.75 × 10−15 m) for hydrogen (the diameter of a single proton)[1] to about 15 fm for the heaviest atoms, such as uranium. These dimensions are much smaller than the diameter of the atom itself (nucleus + electronic cloud), by a factor of about 23,000 (uranium) to about 145,000 (hydrogen). The branch of physics concerned with studying and understanding the atomic nucleus, including its composition and the forces which bind it together, is called nuclear physics.

A figurative depiction of the helium-4 atom with the electron cloud in shades of gray. In the nucleus, the two protons and two neutrons are depicted in red and blue. This depiction shows the particles as separate, whereas in an actual helium atom, the protons are superimposed in space and most likely found at the very center of the nucleus, and the same is true of the two neutrons. Thus, all four particles are most likely found in exactly the same space, at the central point. Classical images of separate particles fail to model known charge distributions in very small nuclei. A more accurate image is that the spacial distribution of nucleons in helium's nucleus, although on a far smaller scale, is much closer to the helium electron cloud shown here, than to the fanciful nucleus image

Introduction Etymology The term nucleus is from the Latin word nucleus , a diminutive of nux ("nut"), meaning the kernel (i.e., the "small nut") inside a fruit. In 1844, Michael Faraday used the term to refer to the "central point of an atom". The modern atomic meaning was proposed by Ernest Rutherford in 1912.[2] The adoption of the term "nucleus" to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article The Atom and the Molecule, that "the atom is composed of the kernel and an outer atom or shell"[3]

Nuclear makeup The nucleus of an atom consists of protons and neutrons (two types of baryons) bound by the nuclear force (also known as the residual strong force). These baryons are further composed of subatomic fundamental particles known as quarks bound by the strong interaction. Which chemical element an atom represents is determined by the number of protons in the nucleus. Each proton carries a single positive charge, and the total electrical charge of the nucleus is spread fairly uniformly throughout its body, with a fall-off at the edge.

Atomic nucleus Major exceptions to this rule are the light elements hydrogen and helium, where the charge is concentrated most highly at the single central point (without a central volume of uniform charge). This configuration is the same as for 1s electrons in atomic orbitals, and is the expected density distribution for fermions (in this case, protons) in 1s states without orbital angular momentum.[4] As each proton carries a unit of charge, the charge distribution is indicative of the proton distribution. The neutron distribution probably is similar.[4]

Protons and neutrons Protons and neutrons are fermions, with different values of the isospin quantum number, so two protons and two neutrons can share the same space wave function since they are not identical quantum entities. They sometimes are viewed as two different quantum states of the same particle, the nucleon.[5] [6] Two fermions, such as two protons, or two neutrons, or a proton + neutron (the deuteron) can exhibit bosonic behavior when they become loosely bound in pairs. In the rare case of a hypernucleus, a third baryon called a hyperon, with a different value of the strangeness quantum number can also share the wave function. However, the latter type of nuclei are extremely unstable and are not found on Earth except in high energy physics experiments. The neutron has a positively charged core of radius ≈ 0.3 fm surrounded by a compensating negative charge of radius between 0.3 fm and 2 fm. The proton has an approximately exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm.[7]

Forces Nuclei are bound together by the residual strong force (nuclear force). The residual strong force is minor residuum of the strong interaction which binds quarks together to form protons and neutrons. This force is much weaker between neutrons and protons because it is mostly neutralized within them, in the same way that electromagnetic forces between neutral atoms (such as van der Waals forces that act between two inert gas atoms) are much weaker than the electromagnetic forces that hold the parts of the atoms internally together (for example, the forces that hold the electrons in an inert gas atom bound to its nucleus). The nuclear force is highly attractive at the distance of typical nucleon separation, and this overwhelms the repulsion between protons which is due to the electromagnetic force, thus allowing nuclei to exist. However, because the residual strong force has a limited range because it decays quickly with distance (see Yukawa potential), only nuclei smaller than a certain size can be completely stable. The largest known completely stable (e.g., stable to alpha, beta, and gamma decay) nucleus is lead-208 which contains a total of 208 nucleons (126 neutrons and 82 protons). Nuclei larger than this maximal size of 208 particles are unstable and (as a trend) become increasingly short-lived with larger size, as the number of neutrons and protons which compose them increases beyond this number. However, bismuth-209 is also stable to beta decay and has the longest half-life to alpha decay of any known isotope, estimated at a billion times longer than the age of the universe. The residual strong force is effective over a very short range (usually only a few fermis; roughly one or two nucleon diameters) and causes an attraction between any pair of nucleons. For example, between protons and neutrons to form [NP] deuteron, and also between protons and protons, and neutrons and neutrons.

88

Atomic nucleus

Halo nuclei and strong force range limits The effective absolute limit of the range of the strong force is represented by halo nuclei such as lithium-11 or boron-14, in which dineutrons, or other collections of neutrons, orbit at distances of about ten fermis (roughly similar to the 8 fermi radius of the nucleus of uranium-238). These nuclei are not maximally dense. Halo nuclei form at the extreme edges of the chart of the nuclides—the neutron drip line and proton drip line—and are all unstable with short half-lives, measured in milliseconds; for example, lithium-11 has a half-life of less than 8.6 milliseconds. Halos in effect represent an excited state with nucleons in an outer quantum shell which has unfilled energy levels "below" it (both in terms of radius and energy). The halo may be made of either neutrons [NN, NNN] or protons [PP, PPP]. Nuclei which have a single neutron halo include 11Be and 19C. A two-neutron halo is exhibited by 6He, 11Li, 17 19 B, B and 22C. Two-neutron halo nuclei break into three fragments, never two, and are called Borromean because of this behavior (referring to a system of three interlocked rings in which breaking any ring frees both of the others). 8 He and 14Be both exhibit a four-neutron halo. Nuclei which have a proton halo include 8B and 26P. A two-proton halo is exhibited by 17Ne and 27S. Proton halos are expected to be more rare and unstable than the neutron examples, because of the repulsive electromagnetic forces of the excess proton(s).

Nuclear models There are many different historical models of the atomic nucleus, none of which to this day completely explains experimental data on nuclear structure.[8] The nuclear radius (R) is considered to be one of the basic things that any model must predict. For stable nuclei (not halo nuclei or other unstable distorted nuclei) the nuclear radius is roughly proportional to the cube root of the mass number (A) of the nucleus, and particularly in nuclei containing many nucleons, as they arrange in more spherical configurations: The stable nucleus has approximately a constant density and therefore the nuclear radius R can be approximated by the following formula,

where A = Atomic mass number (the number of protons, Z, plus the number of neutrons, N) and r0 = 1.25 fm = 1.25 × 10−15 m. In this equation, the constant r0 varies by 0.2 fm, depending on the nucleus in question, but this is less than 20% change from a constant.[9] In other words, packing protons and neutrons in the nucleus gives approximately the same total size result as packing hard spheres of a constant size (like marbles) into a tight spherical or semi-spherical bag (some stable nuclei are not quite spherical, but are known to be prolate).

Liquid drop models Early models of the nucleus viewed the nucleus as a rotating liquid drop. In this model, the trade-off of long-range electromagnetic forces and relatively short-range nuclear forces, together cause behavior which resembled surface tension forces in liquid drops of different sizes. This formula is successful at explaining many important phenomena of nuclei, such as their changing amounts of binding energy as their size and composition changes (see semi-empirical mass formula), but it does not explain the special stability which occurs when nuclei have special "magic numbers" of protons or neutrons.

89

Atomic nucleus

Shell models and other quantum models A number of models for the nucleus have also been proposed in which nucleons occupy orbitals, much like the atomic orbitals in atomic physics theory. These wave models imagine nucleons to be either sizeless point particles in potential wells, or else probability waves as in the "optical model", frictionlessly orbiting at high speed in potential wells. In these models, the nucleons may occupy orbitals in pairs, due to being fermions, but the exact nature and capacity of nuclear shells differs from those of electrons in atomic orbitals, primarily because the potential well in which the nucleons move (especially in larger nuclei) is quite different from the central electromagnetic potential well which binds electrons in atoms. Some resemblance to atomic orbital models may be seen in a small atomic nucleus like that of helium-4, in which the two protons and two neutrons separately occupy 1s orbitals analogous to the 1s orbital for the two electrons in the helium atom, and achieve unusual stability for the same reason. Nuclei with 5 nucleons are all extremely unstable and short-lived, yet, helium-3, with 3 nucleons, is very stable even with lack of a closed 1s orbital shell. Another nucleus with 3 nucleons, the triton hydrogen-3 is unstable and will decay into helium-3 when isolated. Weak nuclear stability with 2 nucleons {NP} in the 1s orbital is found in the deuteron hydrogen-2, with only one nucleon in each of the proton and neutron potential wells. While each nucleon is a fermion, the {NP} deuteron is a boson and thus does not follow Pauli Exclusion for close packing within shells. Lithium-6 with 6 nucleons is highly stable without a closed second 1p shell orbital. For light nuclei with total nucleon numbers 1 to 6 only those with 5 do not show some evidence of stability. Observations of beta-stability of light nuclei outside closed shells indicate that nuclear stability is much more complex than simple closure of shell orbitals with magic numbers of protons and neutrons. For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to the noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows tin to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 (technetium) and 61 (promethium), each of which is preceded and followed by 17 or more stable elements. There are however problems with the shell model when an attempt is made to account for nuclear properties well away from closed shells. This has led to complex post hoc distortions of the shape of the potential well to fit experimental data, but the question remains whether these mathematical manipulations actually correspond to the spatial deformations in real nuclei. Problems with the shell model have led some to propose realistic two-body and three-body nuclear force effects involving nucleon clusters and then build the nucleus on this basis. Two such cluster models are the Close-Packed Spheron Model of Linus Pauling and the 2D Ising Model of MacGregor.[8]

Consistency between models As with the case of superfluid liquid helium, atomic nuclei are an example of a state in which both (1) "ordinary" particle physical rules for volume and (2) non-intuitive quantum mechanical rules for a wave-like nature apply. In superfluid helium, the helium atoms have volume, and essentially "touch" each other, yet at the same time exhibit strange bulk properties, consistent with a Bose-Einstein condensation. The latter reveals that they also have a wave-like nature and do not exhibit standard fluid properties, such as friction. For nuclei made of hadrons which are fermions, the same type of condensation does not occur, yet nevertheless, many nuclear properties can only be explained similarly by a combination of properties of particles with volume, in addition to the frictionless motion characteristic of the wave-like behavior of objects trapped in Schrödinger quantum orbitals.

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Notes [1] Geoff Brumfiel (July 7, 2010). "The proton shrinks in size". Nature. doi:10.1038/news.2010.337. [2] D. Harper. "Nucleus" (http:/ / www. etymonline. com/ index. php?search=Nucleus& searchmode=none). Online Etymology Dictionary. . Retrieved 2010-03-06. [3] G.N. Lewis (1916). "The Atom and the Molecule" (http:/ / osulibrary. oregonstate. edu/ specialcollections/ coll/ pauling/ bond/ papers/ corr216. 3-lewispub-19160400. html). Journal of the American Chemical Society 38 (4): 4. doi:10.1021/ja02261a002. . [4] J.-L. Basdevant, J. Rich, M. Spiro (2005). Fundamentals in Nuclear Physics (http:/ / books. google. com/ ?id=OFx7P9mgC9oC& pg=PA375& dq=helium+ "nuclear+ structure"). Springer. p. 13, Fig. 1.1. ISBN 0387016724. . [5] A.G. Sitenko, V.K. Tartakovskiĭ (1997). Theory of Nucleus: Nuclear Structure and Nuclear Interaction (http:/ / books. google. com/ ?id=swb9QpqOqtAC& pg=PA464& dq=isbn=0792344235#PPA3,M1). Kluwer Academic. p. 3. ISBN 0792344235. . [6] M.A. Srednicki (2007). Quantum Field Theory. Cambridge University Press. pp. 522–523. ISBN 9780521864497. [7] J.-L. Basdevant, J. Rich, M. Spiro (2005). Fundamentals in Nuclear Physics (http:/ / books. google. com/ ?id=OFx7P9mgC9oC& pg=PA375& dq=helium+ "nuclear+ structure"). Springer. p. 155. ISBN 0387016724. . [8] N.D. Cook (2010). Models of the Atomic Nucleus (2nd ed.). Springer. p. 57 ff.. ISBN 978-3-642-14736-4. [9] K.S. Krane (1987). Introductory Nuclear Physics. Wiley-VCH. ISBN 0-471-80553-X.

References • N.D. Cook (2010). Models of the Atomic Nucleus (2nd ed.). Springer. ISBN 978-3-642-14736-4.

External links • The Nucleus - a chapter from an online textbook (http://www.lightandmatter.com/html_books/4em/ch02/ ch02.html) • The LIVEChart of Nuclides - IAEA (http://www-nds.iaea.org/livechart) in Java (http://www-nds.iaea.org/ livechart) or HTML (http://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html) • Article on the "nuclear shell model," giving nuclear shell filling for the various elements (http://www. halexandria.org/dward472.htm). Accessed Sept. 16, 2009.

91

Proton

92

Proton Proton

The quark structure of the proton. (The color assignment of individual quarks is not important, only that all three colors are present.) Classification

Baryon

Composition

2 up quarks, 1 down quark

Statistics

Fermionic

Interactions

Gravity, Electromagnetic, Weak, Strong

Symbol

p, p+, N+

Antiparticle

Antiproton

Theorized

William Prout (1815)

Discovered

Ernest Rutherford (1919)

Mass

1.672621777(74) × 10−27 kg [1] 938.272046(21) MeV/c2 [1] 1.007276466812(90) u

Mean lifetime

>2.1 × 1029 yr (stable)

Electric charge

1 e [1] 1.602176565(35) × 10−19 C

Charge radius

0.8775(51) fm

Electric dipole moment