Phosphorus is a chemical element with symbol P and atomic number 15. Phosphorus is essential for life (compounds containing the phosphate ion) are a component of DNA, RNA, ATP, and phospholipids. Elemental phosphorus exists in many allotropic forms, three major allotropes are white, red and black. Red phosphorus is a component of matchbook strike plates and is used as an ingredient in certain commercial rat and cockroach poisons. Red phosphorus is used in the manufacture of pyrotechnics, safety matches, semiconductors, fertilizers, pesticides, incendiary shells, smoke bombs, and tracer bullets. It is also used in organic synthesis reactions and in the manufacture of phosphoric acid, phosphine, phosphoric anhydride, phosphorus pentachloride, and phosphorus trichloride. Red phosphorus is also used in electroluminescent coatings and in flame retardants for polymers.