Phosphorus is a highly reactive chemical that has four forms, red, white, purple/red and red/black.

White phosphorus will burn up on contact with air or with toxins. Another type of phosphorus is red phosphorus, which is formed by either exposing white phosphorus to sunlight or heating white phosphorus to 250C/482F. Red phosphorus will not catch on fire in the air in temperatures below 240C, but white phosphorus will ignite in the air at 30C.

Purple/red phosphorus or commonly known as "Hittorf's phosphorus" is formed when phosphorus is recrystallized from molten lead. Another form is a red/black phosphorus which is a cubic solid, that has an orthorhombic structure and is also the least reactive allotrope. It consists of many six-membered rings which are interlinked, each atom is bonded to three other atoms. A recent synthesis of black phosphorus using metal salts as catalysts has been reported.

Phosphorus has a faint glow that was discovered in 1669, but it wasn't fully described until 1974. This was because of the oxygen being consumed by the phosphorus. But it was later discovered that it does not glow in pure oxygen, only a range of partial pressure at which it glows. In 1974 the glow was explained with it being a reaction with oxygen that forms the short-lived HPO and P2O2 that both emit the visible light. The reaction is slow and very little of the intermediates is required to produce the luminescence.

Because of its high reactivity with air and other oxygen-containing substances phosphorus is not found free in nature but is widely distributed in many different minerals. Phosphate rock being the most common commercial source for it, which is partially made up of apatite. Around 50% of the global phosphorus reserves are in the Arab nations. With todays rate of consumption the global supply of phosphorus is estimated to last for another 300-345 years.

Phosphorus has many uses, such as fertilizer, plasticizers, flame retardants, pesticides, extraction agents, water treatment, a very important component in steel production, the glass for sodium lamps, fine china, laundry detergents, food and beverages, cooking ingredients, incendiary bombs, smoke-screening, tracer ammunition, matchbook strikers, flares, safety matches, cap gun caps, used in the heads of strike-anywhere matches, N-type semiconductors, radioactive tracers for biochemical laboratories, and many other applications.

Phosphorus is a key element in all known life forms. Inorganic phosphorus in the form of phosphate PO4-3 plays a major role in biological molecules such as DNA and RNA where it forms part of the structural framework of these molecules. Living cells also use phosphate to transport cellular energy via adenosine triphoshate (ATP). Nearly every cellular process that uses energy obtains it in the form of ATP. The average adult contains 1 kg of phosphorus, around 85% is in the bones and teeth in the form of apatite, the remainder inside cells in soft tissues.