Phosphorus and Its Modification

**Symbol:** P **Atomic number:** 15 **International name:** Phosphorus **General formula:** P₄ **Relative Atomic Weight:** 30.974 **Description:** Phosphorus is a non-metal that exists in several allotropic forms, the most common being white, red, and black phosphorus. White phosphorus is composed of tetrahedral P₄ molecules and is a highly toxic and reactive substance of yellowish color. It is unstable and can spontaneously ignite in air. Red phosphorus is a relatively stable, non-toxic substance with a polymeric structure. Black phosphorus is the most stable allotrope and exhibits properties closer to those of metals. **Applications:** Red phosphorus is used in the production of matches and as a raw material in the chemical industry. **Occurrence:** Phosphorus occurs naturally only as a phosphorus compound, mainly as phosphates. The most significant phosphorus mineral is apatite (Ca₅(PO₄)₃X, where X can be OH, F or Cl), and phosphorite (Ca₃(PO₄)₂). Phosphorus is an essential biogenic element, present in nucleic acids and as phospholipids in biological membranes.