Formulae of compounds containing group ions

Chemical formulaeFormulae of compounds containing group ions

The chemical formula for a substance shows how many atoms of each element are present in a molecule, or the proportion of atoms of each element. The formula can be worked out using the valency.

Group ions contain two or more atoms and usually have a negative charge. The formulae of these ions can be found in the data booklet. We can take the number of charges on the ion as the valency of the ion.