The charge of phosphorus depends on whether it is an ion or an atom. Phosphorus has 15 protons in its nucleus, which gives it a positive charge of 15. However, since it also has 15 electrons, the overall charge of a phosphorus atom is neutral. When phosphorus forms an ion, it typically gains three electrons to form a negative ion with a charge of -3, known as the phosphide ion. Therefore, the charge of phosphorus depends on whether it is an ion or an atom, and in the case of an ion, it has a charge of -3.