Phosphorus is a chemical element in the nitrogen group identified by the symbol P on the periodic table of elements. The nonmetallic element is extremely reactive and also highly toxic, although it is also an important trace mineral in most living organisms. There are numerous uses for phosphorus compounds, and most people interact with some form of the element every day. When you strike a match, fertilize the garden, or use most electronics, phosphorus is involved.

The discovery of phosphorus is credited to Hennig Brandt, an alchemist who successfully isolated it from urine in the late 1660s. Brandt noted that his discovery possessed the curious property of glowing when it was exposed to air, and he named it phosphorus after the Greek phosphoros, meaning “evening star.” The atomic number of phosphorus is 15, placing it among the lighter chemical elements, and it is rarely if ever found in a pure form.

Like other elements in the nitrogen group, a peculiarity of the structure of phosphorus causes it to make very strong bonds with other elements. In addition to making the element highly reactive, this also ensures that it appears in numerous compounds. One of the most important groups of phosphorus compounds is the phosphates. There are numerous examples of phosphates; you are probably familiar with calcium phosphate, the mineral which composes the bulk of your bone structure.

Along with several other elements, phosphorus exhibits allotropy, meaning that its pure form can appear in a number of ways in the same state. Carbon is another such element, appearing in the radically different but still pure forms of diamond and coal. Phosphorus has three allotropes; white, red, and black. White phosphorus is the most toxic and reactive of the three, appearing as a waxy solid which ranges in color from white to yellow.

When exposed to air, white phosphorus will begin to burn, and the element also glows in the dark. Exposure to heat or light will turn white phosphorus into red phosphorus, a much more stable allotrope which is used to make things like matches. If white phosphorus is heated under pressure, it turns into black phosphorus. All of these forms are pure phosphorus, but they look and behave very differently.

In addition to matches, phosphorus is also used in incendiary devices, fertilizers, and fireworks. Some products may sport an anti-corrosive coating made of phosphorus, and the element is used as a dopant in electronics manufacturing as well. Since the element is toxic, pure forms should be handled with care, as should many phosphorus compounds.