SPM Chemistry Form 4 Notes

SPM Chemistry Form 4 Notes – Chemical Bonds (Part 1) Formation of Compounds   

Compounds – different elements that chemically bonded together Octet electron arrangement – electron arrangement of an atom where the outermost occupied shell is filled with eight valence electrons Duplet electron arrangement – electron arrangement of an atom where a single shell filled with two valence electrons

Example: Compound water is hydrogen and oxygen atoms are chemically bonded together. Stability of Noble Gases    

Atom of noble gas does not gain, lose nor share electrons with other atoms. Noble gas atoms do not combine with atoms of other elements to form compounds or with each other to form molecules. Noble gases are chemically unreactive. Noble gases exist as monoatomic.

Chemical Bonds

Chemical Bond Types of chemical bonds:  

ionic bonds (metal + non-metal) covalent bonds (non-metal + non-metal)

Atoms of other elements can achieve the stable octet electron arrangement by  

transfer of electrons sharing of electrons

Scientist Italian physicist Amedeo Avogadro (Name at birth: Lorenzo Romano Amedeo Carlo Avogadro)    

Born: 9 August 1776 Birthplace: Turin, Piedmont, Italy Died: 9 July 1856 Best Known As: The guy they named Avogadro’s number after

1. Avogadro constant / Avogadro’s number is 6.02 x 1023 2. Atomic substances   

Elements – all the particles are atoms. Example: zinc (Zn), sodium (Na), aluminium (Al) and all noble gases, argon (Ar), helium (He) and neon (Ne). RAM (Relative Atomic Mass) of Na = 23

3. Molecular substances   

Covalent compounds – the particles are molecules. Example: carbon dioxide (CO2), water (H2O) and non-metal elements, iodine (I2), nitrogen (N2) and oxygen (O2). RMM (Relative Molecular Mass) of I2 = 127 + 127 = 254

4. Ionic substances   

Ionic compounds – the particles are ions. Example: sodium chloride (NaCl), hydrochloric acid (HCl) and potassium iodide (KI). RFM (Relative Formula Mass) of HCl = 1 + 35.5 = 36.5

5. Avogadro’s Law / Gas Law states that equal volumes of all gases contain the same number of molecules under the same temperature and pressure. 

Example: equal volumes of molecular hydrogen and nitrogen would contain the same number of molecules under the same temperature and pressure.

6. Volume of gas (dm3) = Number of moles of gas x Molar volume 7. Room temperature and pressure (r.t.p.) = 24 dm3 mol-1 (25°C and 1 atm)  

Example: What is the volume of 5.0 mol helium gas at s.t.p.? Volume of gas = Number of moles x Molar gas volume = 5.0 mol x 24 dm3 mol-1 = 120 dm3

8. Standard temperature and pressure (s.t.p.) = 22.4 dm3 mol-1 (0°C and 1 atm)

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Example: What is the volume of 5.0 mol helium gas at s.t.p.? Volume of gas = Number of moles x Molar gas volume = 5.0 mol x 22.4 dm3 mol-1 = 112 dm3

9. Mass (g) = Number of moles x Molar mass 10. Number of particles = Number of moles x Avogadro constant 11. Volume (dm3) = Number of moles x Molar volume Be sure to copy down all these formulae a few times on paper so that you will have a better chance recalling it in the future. Copying them onto a card to bring around will be very helpful.

Empirical and Molecular Formulae 1. Empirical (simplest ratio of atoms of each element that present in the compound) and molecular formulae (actual number of atoms of each element that are present in one molecule of the compound) indicate:   

the types of the elements the symbols of the elements and the ratio of atoms or moles of atoms of each element in a compound.

2. Molecular formula = (empirical formula)n n is a positive number Compound Carbon dioxide Ethane Propene Glucose Quinine

Molecular formula CO2 CH3 CH2 CH2O C10H12NO

n 1 2 3 6 2

Empirical formula (CO2) = CO2 (CH3)2 = C2H6 (CH2)3 = C3H6 (CH2O)6 = C6H12O6 C20H24N2O2

3. Chemical formulae for covalent compounds. Name Nitrogen gas

Chemical Number of each element formula N2 2 nitrogen atoms

Oxygen gas Ammonia

O2 NH3

Water

H2O

2 oxygen atoms 1 nitrogen atom and 3 hydrogen atoms 2 hydrogen atoms and 1 oxygen atom

4. Cations are positively-charged ions. Charge +1 +1 * +1 +1 +1 * +1 +1 +1 +2 +2 +2 * +2 * +2 * +2 +2 * +2 +2 * +2 +3 +3 * +3 * +4 * +4 *

Cations Ammonium ion Copper(I) ion Hydrogen ion Lithium ion Nickel(I) ion Potassium ion Silver ion Sodium ion Barium ion Calcium ion Copper(II) ion Iron(II) ion Lead(II) ion Magnesium ion Manganese(II) ion Nickel(II) ion Tin(II) ion Zinc ion Aluminium ion Chromium(III) ion Iron(III) ion Lead(IV) ion Tin(IV) ion

Formula NH4+ Cu+ H+ Li+ Ni+ K+ Ag+ Na+ Ba2+ Ca2+ Cu2+ Fe2+ Pb2+ Mg2+ Mn2+ Ni2+ Sn2+ Zn2+ Al3+ Cr3+ Fe3+ Pb4+ Sn4+

* refer to the Roman numerals 5. Anions are negatively-charged ions. Charge -1 -1 -1 -1 -1 -1 -1 -1

Anions Bromide ion Chloride ion Chlorate(V) ion Ethanoate ion Fluoride ion Hydride ion Hydroxide ion Iodide ion

Formula BrClClO3CH3COOFHOHI-

-1 -1 -1 -2 -2 -2 -2 -2 -2 -2 -2 -3 -3 -3

Manganate(VII) ion Nitrate ion Nitrite ion Oxide ion Carbonate ion Chromate(VI) ion Dichromate(VI) ion Sulphide ion Sulphate ion Sulphite ion Thiosulphate ion Nitride ion Phosphate ion Phosphite ion

MnO4NO3NO2O2CO32CrO42Cr2O72S2SO42SO32S2O32N3PO43PO33-

6. Chemical formulae for ionic compounds Name

Chemical formula

Zinc chloride Copper(II) sulphate Aluminium sulphate

ZnCl2 CuSO4 Al2(SO4)3

Number of cation 1 Zn2+ 2 Cu2+ 2 Al3+

Number of anion 2 Cl2 SO423 SO42-

7. Meaning of prefixes Prefix MonoDiTriTetraPentaHexaHeptaOctaNonaDeca-

Meaning 1 2 3 4 5 6 7 8 9 10

8. Naming of chemical (non-metal) compounds with Greek numerical prefixes. Non-metal compound Carbon monoxide Carbon dioxide Sulphur dioxide Sulphur trioxide Carbon tetrachloride (tetrachloromethane)

Chemical formula CO CO2 SO2 SO3 CCl4

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Chemical Equation 1. Importance of chemical equation: The types of reactants; the physical conditions; the quantity of reactants and products and stated in moles. nA + nB –> pC + pD 2. Reactants are written in the left side of the reaction and products are written in the right side of the reaction. 

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Example 1: Word equation: Sodium hydroxide + sulphuric acid –> sodium sulphate + water Chemical equation: NaOH + H2SO4 –> Na2SO4 + H2O Balancing equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O Complete chemical equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O Example 2: Word equation: Aluminium + copper(II) oxide –> aluminium(III) oxide + copper Chemical equation: Al + CuO –> Al2O3 + Cu Balancing equation: 2Al + 3CuO –> Al2O3 + 3Cu Complete chemical equation: 2Al + 3CuO –> Al2O3 + 3Cu Example 3: Word equation: Nitrogen + hydrogen ammonia Chemical equation: N2 + H2 NH3 Balancing equation: N2 + 3H2 2NH3 Complete chemical equation: N2 + 3H2 2NH3

3. Information obtainable from chemical equations.    

i) mass of reactants ii) volume of reacting gas iii) mass of products formed iv) volume of gas produced

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Example: 2 cm3 of lead (II) nitrate solution is added to excess of potassium iodide solution. How many molecules of potassium nitrate will be formed?

[Relative atomic mass: N, 14; O, 16; K, 39; I, 127; Pb, 207; Avogadro's constant: 6.02 x 1023 mol-1] Step 1: Write a complete chemical equation.  

Pb(NO3)2(aq) + 2KI(aq) –> PbI2(s) + 2KNO3(aq) From the equation, 1 mole of Pb(NO3)2 reacts with 2 moles of KI formed 1 mole PbI2 of and 2 moles of KNO3.

Step 2: Convert to moles. 

No. of moles of Pb(NO3)2 = Mass of Pb(NO3)2 / Relative molecular mass = 2 / [207 + 2(14 + 3 x 16)] = 6.04 x 10-3 mol

Step 3: Ratio of moles.  

Number of moles of KNO3/ Number of moles of Pb(NO3)2 = 2/1 Number of moles of KNO3 = (2 x 6.04 x 10-3) / 1 = 12.08 x 10-3 mol

Step 4: Convert to the number of molecules of potassium nitrate. 

Number of molecules of KNO3 = 12.08 x 10-3 x 6.02 x 1023 = 7.27 x 1021

Once you have completed all parts in this series, you would have mastered the most basic of knowledge in SPM Chemistry. So make sure all Readers understand the basics before moving on to more advance topics.

SPM Chemistry Form 4 Notes – Periodic Table of Elements (Part 1) Development of the Periodic Table

Periodic Table A) Antoine Lavoisier (1743 – 1794) – French chemist  

Elements were classified into 4 groups Limitation – some wrong information (light and heat were consider as elements

B) Johann Dobereiner (1780 – 1849) – German chemist  

Elements were classified into groups named as triad (Triad Law – relationship between properties and atomic masses of the elements) Limitation – few elements were classified

C) John Newlands (1837 – 1898) – British chemist 

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Elements were arranged horizontally in ascending order of their atomic masses and each row consisted of 7 elements (Law of Octaves – same properties were repeated at every eight element) Limitation – obeyed by the first 17 elements only (from H to Ca)

D) Lothar Meyer (1830 – 1895) – German chemist  

Properties of the elements were in a periodic pattern with their atomic masses Similar chemical properties occupied the same relative positions on the curve

E) Dmitri Mendeleev (1834 – 1907) – Russian chemist     

Elements were arranged in ascending order of their atomic masses Elements with similar chemical properties were placed in a group Gap for undiscovered elements Prediction: gallium, scandium and germanium (discover later) Separate groups for certain elements: transition elements

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Meedeleev’s Periodic Table was used as a basis for the formation of the Periodic Table

F) H. J. G. Moseley (1887 – 1915) – British physicist                    

Elements were arranged horizontally in ascending order – proton numbers Elements with the same number valence electrons – same group 18 vertical columns – Group 1, Group 2, until Group 18 Alkali metal – Group 1 Alkaline earth metal – Group 2 Transition elements – Group 3 to Group 12 Halogen – Group 17 Noble gas – Group 18 Horizontal row of the elements – period Period 1 – 2 elements Period 2 and 3 – 8 elements Period 4 and 5 – 18 elements Period 6 – 32 elements Period 7 – 27 elements Lantanides – proton numbers 58 to 71 Actinides – proton numbers 90 to 103 Elements (Group 1, 2 and 13) – metal Transition elements (Group 3 to 12) – metal Elements (Group 15, 16 and 17) – non-metal Carbon and silicon (Group 14) – non-metal

The next part, Part 2 Notes on Periodic Table of Elements for SPM Chemistry students will focus on the relationship between electron arrangement of the atom of an element to its group and period. It’s easy for a Form 5 student when they look back but rather difficult for a Form 4 student. So Form 4 students need to pay full attention when your teacher is teaching this part, or you can always refer back to Berry Berry Easy for our notes