3.4 Polyatomic Ions and Predicting Bond Types

Polyatomic Ions

When previously discussing ionic bonds, they were only considered in the context of two elements being bonded, such as FeS being a bond between ${Fe^{2+}}$ and ${S^{2-}}$. However, ionic compounds do not have to consist of solely 2 elements. Polyatomic ions are groups of atoms that are covalently bonded to each other yet contain an overall charge. For example, in the polyatomic ion hydroxide, or OH–, the oxygen and hydrogen atoms are covalently bonded. However, the entire molecule contains a charge of 1–. This means that it can bond with a cation. For example, the formula for potassium hydroxide is KOH.