Introduction to bonding

This section will look at three types of bonding that are often discussed in chemistry. These are:

• Covalent bonding
• Ionic bonding
• Metallic bonding

There is a very important relationship between the type of bond and an atom's electronegativity, or it's ability to attract electrons. Highly electronegative atoms will attract electrons more strongly than electropositive atoms.

It is possible to make a prediction about the type of bond an atom is likely to favour, and other atoms or ions it is likely to bond with, once we know how electronegative or electropositive it is. 

Consider a molecule or compound A_mB_n (where A and B are different elements). Allow A and B to vary from being highly electronegative to highly electropositive. 

A and B are electropositive: There is low electron attraction and therefore electrons are easily lost from individual atoms. The negatively charged electrons are able to move freely throughout the solid between positively charged ions; this is known as an electron sea, which results in metallic bonding.

A is electropositive and B is electronegative: As electrons are easily lost by A and strongly attracted to B, the ions A⁺ and B^- are formed. The ions are held together by electrostatic interactions to produce ionic bonding.

A and B are electronegative: Neither A or B lose their electrons easily. It is easier therefore, for atoms to share electrons in order to complete their valence shell.

Not many compounds lie at the corners of the triangle. The majority of compounds are found in the intermediate regions.