What charge does a phosphate ion carry?

A phosphate ion carries a charge of -3. Phosphate is a polyatomic ion, often represented as PO4^3-. The phosphorus atom is bonded to four oxygen atoms, and in this arrangement, the overall charge results from the loss of three electrons, leading to an additional negative charge.

In more detail, each oxygen atom typically has a -2 charge in compounds, but in the phosphate ion, the total contributions of the oxygen atoms result in a net charge of -3 after accounting for the bonding structure and the oxidation states involved. This characteristic makes the phosphate ion an important polyatomic ion in biological systems, particularly in energy transfer and storage as part of molecules like ATP (adenosine triphosphate) and in the structure of DNA and RNA.