Question

define:diatomic ion,triatomic ion and polyatomic ion

Answer 1

diatomic means it consists of two atoms
triatomic means three kinds of atoms
poly atomic means more than three kinds of atoms

Answer 2

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.