Question

Why is a polyatomic ion not called a molecule?

Answer 1

Polyatomic ions contain two or more atoms bonded together in a manner that there is still a charge on the molecule.

Monatomic ions are charged atoms of single element,

Examples of monatomic ions include, sodium ions are `Na^+` and Fluoride ions are `F^-`,

However, examples of polyatomic ions are `NO_3^-`, `PO_4^(-3)` and `NH_4^+`. In each case the ion is composed of more than one atom.

I hope this was helpful.
SMARTERTEACHER