Phosphate ion (PO₄³⁻)

Phosphate is one phosphorus atom bonded to four oxygen atoms, with a 3− charge. Phosphoric acid, H₃PO₄, has three hydrogen ions to give, and when all three are gone the ion carries three negative charges. Phosphate is in fertilizers, in the backbone of DNA and in the mineral that makes bones and teeth hard.

• Adding H⁺ step by step gives hydrogen phosphate, HPO₄²⁻, and then dihydrogen phosphate, H₂PO₄⁻.
• Arsenate, AsO₄³⁻, has the same shape and charge because arsenic sits just below phosphorus in group 15.
• Trisodium phosphate, Na₃PO₄, is a strong cleaner used to wash walls before painting.

Compounds that contain phosphate

Other ions with a −3 charge