What is a polyatmic atom?

polyatomic ion is a charged chemical species composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit.

A polyatomic ion, also known as a molecular ion, is a charged chemical species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit. The prefix poly - means "many," in Greek, but even ions of two atoms are commonly referred to as polyatomic.