* Electron Configuration: Phosphorus has 5 valence electrons (electrons in its outermost shell).
* Stability: Atoms strive to achieve a stable electron configuration, typically resembling the nearest noble gas. The nearest noble gas to phosphorus is argon (Ar), which has 8 valence electrons.
* Gaining Electrons: To achieve a stable octet, phosphorus needs to gain 3 electrons. This gain of electrons results in a negative charge.
Therefore, phosphorus forms a phosphide ion (P³⁻) by gaining three electrons.
