These are various compounds and ions related to phosphorus and calcium chemistry.

P: Phosphorus, a non-metal elementP2O5: Phosphorus pentoxide, a chemical compound also known as diphosphorus pentoxideH3PO4: Phosphoric acid, a mineral acid with the chemical formula H3PO4Ca3(PO4)2: Calcium phosphate, a chemical compound commonly found in bone tissueCa(OH)2: Calcium hydroxide, also known as slaked lime, a chemical compoundCaO: Calcium oxide, also known as quicklime, a chemical compoundCaC2: Calcium carbide, a chemical compound used in the production of acetylene gas