How does an binary compound different from an polyatomic ion?

A binary compound is a chemical compound made up solely of 2 elements, for example P2O5, Na2O KCl. (The bonding is not relevant- it could be covalent or ionic.)

A polyatomic ion is a cation or anion that contains more than one atom. Most contain 2 different elements. For example

• polyatomic anions:- [SO4]2-, [NO3]-
• polyatomic cation:-[ NH4]+ , [Hg2]2+