15PPhosphorus

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Phosphorus is a chemical element; it has symbol P and atomic number 15. All elemental forms of phosphorus are highly reactive and are therefore never found in nature. They can nevertheless be prepared artificially, the two most common allotropes being white phosphorus and red phosphorus. With 31P as its only stable isotope, phosphorus has an occurrence in Earth's crust of about 0. 1%, generally as phosphate rock. A member of the pnictogen family, phosphorus readily forms a wide variety of organic and inorganic compounds, with as its main oxidation states +5, +3 and −3.

The isolation of white phosphorus in 1669 by Hennig Brand marked the scientific community's first discovery of an element since Antiquity. The name phosphorus is a reference to the god of the Morning star in Greek mythology, inspired by the faint glow of white phosphorus when exposed to oxygen. This property is also at the origin of the term phosphorescence, meaning glow after illumination, although white phosphorus itself does not exhibit phosphorescence, but chemiluminescence caused by its oxidation. Its high toxicity makes exposure to white phosphorus very dangerous, while its flammability and pyrophoricity can be weaponised in the form of incendiaries. Red phosphorus is less dangerous and is used in matches and fire retardants.

Most industrial production of phosphorus is focused on the mining and transformation of phosphate rock into phosphoric acid for phosphate-based fertilisers. Phosphorus is an essential and often limiting nutrient for plants, and while natural levels are normally maintained over time by the phosphorus cycle, it is too slow for the regeneration of soil that undergoes intensive cultivation. As a consequence, these fertilisers are vital to modern agriculture. The leading producers of phosphate ore in 2024 were China, Morocco, the United States and Russia, with two-thirds of the estimated exploitable phosphate reserves worldwide in Morocco alone. Other applications of phosphorus compounds include pesticides, food additives, and detergents.

Phosphorus is essential to all known forms of life, largely through organophosphates, organic compounds containing the phosphate ion PO3−4 as a functional group. These include DNA, RNA, ATP, and phospholipids, complex compounds fundamental to the functioning of all cells. The main component of bones and teeth, bone mineral, is a modified form of hydroxyapatite, itself a phosphorus mineral.