The formula H₂PO₄²⁻ is chemically incorrect because the dihydrogen phosphate ion (H₂PO₄⁻) carries a single negative charge, not two. The correct representation is H₂PO₄⁻, which is the conjugate base of phosphoric acid (H₃PO₄) and the conjugate acid of hydrogen phosphate (HPO₄²⁻).