Final answer:
The polyatomic ions PO4³⁻ and PO3³⁻ adhere to naming rules based on oxygen content; PO4³⁻ with more oxygen is 'phosphate' (-ate), while PO3³⁻ being 'phosphite' (-ite).
Step-by-step explanation:
The naming of polyatomic ions with PO4³⁻ and PO3³⁻ depends on the suffixes used to distinguish the differing amounts of oxygen atoms they contain. In accordance with inorganic nomenclature rules, the ion with more oxygen atoms will have the name ending in -ate, and the ion with fewer oxygen atoms will have the name ending in -ite. Hence, PO4³⁻ is referred to as phosphate, and PO3³⁻ is called phosphite. To remember these, it is essential to memorize the combinations as the system only indicates the relative number of oxygen atoms in the ions.