The concept of a covalent bond together with the noble gas rule now allows us to predict the possible molecules made up of non metals. The noble gas rule works especially well for molecules containing carbon, nitrogen, oxygen and hydrogen. It works well for other elements also, however there are exceptions that must be considered. It may seem as though we are severly limited if we can reliably apply the noble gas rule only to molecules with the above four elements. Fortunately, however, most common molecules involve only these four elements.

The noble gas rule as applied to molecules is simple: Every atom in a molecule seeks to attain a noble gas electronic configuration around it.

Consider the electron dot structure of methane: