Chemical bond

A mutual electrical attraction between the nuclei and valence

electrons of different atoms that binds the atoms together.

Why Bond?

• Potential energy is lowered

• More stable

Types of bonds

• Ionic

• Covalent

• metallic

Ionic bonding

• Bonding that results from the electrical attraction between large numbers of cations and anions.

Covalent bonding

• Results from the sharing of electrons pairs between two atoms.

Metallic bonding

• Bonding that results from the attraction between metal atoms and the surrounding “sea of electrons”

– Delocalized electrons – electrons that freely move around; empty orbitals overlap, electrons very mobile making a “sea” of electrons

How can you tell if a bond is ionic or covalent?

• A bond is rarely purely ionic or covalent. Usually falls somewhere between the two extremes.

• Diatomic – covalent

electronegativity• Measure of an atom’s ability to attract

electrons.

• The degree to which bond is ionic or covalent depends on the difference in electronegativities.

How to do

• Look up the electronegativities of the atoms involved on a chart.

• Subtract the two numbers

• Find where they fall on the ionic- covalent scale.

Polar

• Polar – an unequal sharing of electrons that lends a molecule to be partially negative at one end and partially positive at another. Water is an example.

Reading the chart

• Values above 1.7 are ionic, the closer you are to 3.3 the more ionic.

• Values under 1.7 are covalent.– Values under 0.3 are nonpolar -covalent– Values between 1.7 and .3 are polar -covalent