How do polyatomic ions bond?

are covalently bonded within the ion, but they form ionic bonds to other ions.

The only difference between a molecule and an ion is the number of .

Since molecules are covalently bonded, their polyatomic ions are also covalently bonded.

For example, in the Lewis structure of sulfate ion, ##"SO"_4^"2-"##, the bonds between the S and O atoms are all covalent.

Once the sulfate ion, ##"SO"_4^"2-"## has formed, it can form ionic bonds by electrostatic attractions to positive ions such as ##"Na"^+## and form the ionic compound ##"Na"_2"SO"_4##.