The formula for the phosphide ion is Pb^3-.
Phosphide is an anion formed when phosphorus gains three electrons, leading to a negative charge. In chemical notation, this is represented as P^{3-}. This ion typically originates from phosphorus atoms, which are found in group 15 of the periodic table. The phosphide ion is important in various chemical reactions and compounds, particularly in forms like metal phosphides used in semiconductors and other materials. Always remember that the charge of the ion plays a crucial role in understanding its behavior in chemical processes.