Structure of sulfides

Semimetals (metalloids) and some nonmetallic elements form sulfides that are molecular or that have sulfide bridges in a polymeric structure. For example, silicon disulfide, SiS₂, has a structure consisting of infinite chains of SiS₄ tetrahedrons that share edges. (Each SiS₄ tetrahedron consists of a central silicon atom surrounded by and bonded to four sulfur atoms.) Phosphorus forms a series of molecular sulfides that includes P₄S₃, P₄S₄ (two distinct forms), P₄S₅, P₄S₇, P₄S₉, and P₄S₁₀. The structures of all these compounds are derived from a P₄ tetrahedron in which P―P bonds are replaced by P―S―P units. All these phosphorus sulfides are stable in carbon disulfide (CS₂), and all react with water to produce phosphoric acid (H₃PO₄) or other phosphorus oxyacids.P₄S₁₀ + 16H₂O → 4H₃PO₄ + 10H₂SThe tips of strike-anywhere matches contain P₄S₃, which ignites in air as a result of the friction produced when the match is rubbed against a rough surface. A flame is produced by reaction of the phosphorus sulfide with active chemicals in the match head. P₄S₁₀ is used in the preparation of industrial lubricant additives.