What is the charge of a phosphate ion?

The phosphate ion, commonly represented as PO₄³⁻, carries a charge of -3. This comes from the structure of the ion itself. Phosphorus, the central atom, typically has five valence electrons, while each oxygen atom contributes six, giving a total of 24 valence electrons for a neutral PO₄ molecule. However, in forming the phosphate ion, the molecule gains additional electrons due to the tendency for the molecule to bond more stably in this form.

Each of the four oxygen atoms tends to form a bond and complete its octet, creating an overall negative charge. When considering the total charge, phosphorus effectively gives up positive charge by disproportionally influencing the bonding situation with the oxygens, leading to a net charge of -3.

In summary, the phosphate ion is characterized by its -3 charge because of the way the atoms combine and stabilize when additional electrons are acquired.