Which category does the ion PO43 - belong to? monatomic cation monatomic anion polyatomic anion polyatomic cation monatomic ion

PO4³⁻ (phosphate anion) is a polyatomic anion which first of all means that he has more then one atom in his structure. ³⁻ means that he is negatively charged, so that's why he is an anion. ³⁻ also means that he has 3 extra electrons, 3 more electrons than there are protons in the nuclei of a phosphorus atom plus oxygen atoms.