chemical bond types

Chemical Bond Types

Ionic Bonds

An ionic bond is formed by the attraction of oppositely charged atoms or groups of atoms. When an atom (or group of atoms) gains or loses one or more electrons, it forms an ion. Ions have either a net positive or net negative charge. Positively charged ions are attracted to the negatively charged 'cathode' in an electric field and are called cations. Anions are negatively charged ions named as a result of their attraction attraction to the positive 'anode' in an electric field. Every ionic chemical bond is made up of at least one cation and one anion. Ionic bonding is bonding is typically described to students as being the outcome of the transfer of electron(s) beteen to dissimilar atoms. !he "eis structure belo illustrates this concept.

#or binary atomic systems, ionic bonding typically occurs beteen one metallic atom and one nonmetallic atom. !he

electronegativity difference beteen the highly electronegative nonmetal atom and the metal atom indicates the potential for electron transfer. $odium chloride (%a&l) is the classic eample of eample of ionic bonding. Ionic bonding is not isolated to simple binary systems, hoever. An ionic bond can occur at the center of a large covalently bonded organic molecule such as an enyme. In this case, a metal atom, lie iron, is both covalently bonded to large carbon groups and ionically bonded to other simpler inorganic compounds (lie oygen). *rganic functional groups, lie the carboylic acid group depicted belo, contain covalent bonding in the carboyl portion of the group (+&**) hich itself serves as the anion to the acidic hydrogen ion (cation).

Covalent

A covalent chemical bond results from the sharing of electrons beteen to atoms ith similar electronegativities A single covalent bond represent the sharing of to valence electrons (usually from to different atoms). !he "eis structure belo represents the covalent bond beteen bond beteen to hydrogen atoms in a + molecule.

Dot Structure

Line Structure

-ultiple covalent bonds are common for certain atoms depending upon their valence configuration. #or eample, a double covalent bond, hich occurs in ethylene (&+), results from the sharing of  to sets of valence electrons. Atomic nitrogen (%) is an eample of a triple covalent bond. Double Covalent Bond 

Triple Covalent Bond 

!he polarity of a covalent bond is defined by any difference in electronegativity the to atoms participating. Bond polarity describes the distribution of electron density around to bonded atoms. #or to bonded atoms ith similar electronegativities, electronegativities, the electron density of the bond is e/ually distributed beteen the to atom is !his is a nonpolar covalent bond. !he electron density of a covalent bond is shifted toards the atom ith the largest electronegativity. electronegativity. !his results in a net negative charge ithin the bond favoring the more electronegative atom and a net positive charge for the least electronegative atom. !his is a polar covalent bond.

Coordinate Covalent

A coordinate covalent bond (also bond (also called a dative bond) is formed hen one atom donates both of the electrons to form a single covalent bond. !hese electrons originate from the donor atom as an unshared pair.

0oth the ammonium ion and hydronium ion contain one coordinate covalent covalent bond each. A lone pair on the oygen atom in ater contributes to electrons to form a coordinate covalent bond ith a hydrogen ion to form the hydronium ion. $imilarly, a lone pair on nitrogen contributes  electrons to form the ammonium ion. All of the bonds in these ions are indistinguishable once formed, hoever.

Ammonium (NH 4+)

Hydronium (H3O+)

Network Covalent

$ome elements form very large molecules by forming covalent bonds. When these molecules repeat the same structure over and over in the entire piece of material, the bonding of the substance is called netor covalent. 1iamond is an eample of carbon bonded to itself. Each carbon forms  covalent bonds to  other carbon atoms forming one large molecule the sie of each crystal of diamond.

$ilicates, 2$i*3 also form these netor covalent bonds. $ilicates are found in sand, /uart, and many minerals.

Metallic

!he valence electrons of pure metals are not strongly associated ith particular atoms. !his is a function of their lo ioniation energy. Electrons in metals are said to be delocalized (not found in one specific region, such as beteen to particular atoms). $ince they are not confined to a specific area, electrons act lie a floing 4sea5, moving about the positively charged cores of the metal atoms. •

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1elocaliation can be used to eplain conductivity, malleability, and ductility. 0ecause no one atom in a metal sample has a strong hold on its electrons and shares them ith its neighbors, e say that they are bonded. In general, the greater the number of electrons per atom that participate in metallic bonding, the stronger the metallic bond.