Phosphorus was discovered in 1669 by Hennig Brand, a German alchemist in Hamburg who was searching for the “philosopher’s stone.” He boiled down large amounts of urine and heated the residue, producing a white, waxy substance that glowed eerily in the dark.
Brand was the first person in recorded history known to discover an element. He kept his method secret for several years, and other chemists, including Robert Boyle, later worked out how to make phosphorus themselves. The name comes from the Greek word ‘phosphoros’, meaning “light-bearer,” because white phosphorus glows when it reacts with oxygen in the air.
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- Symbol: P
- Atomic Number: 15
- Atomic Weight: 30.974
- Element Classification: Non-metal
- Discovered By: Hennig Brand
- Discovery Date: 1669
- Name Origin: Greek: ‘phosphoros’ meaning “light-bearer”
- Density(g/cc): 1.823 (white phosphorus)
- Melting Point: 44.15°C (white phosphorus)
- Boiling Point: 280.5°C
- Appearance: White, red or black solid; white phosphorus is waxy and glows in the dark
- Atomic Radius(pm): 100
Relation to Other Elements
Phosphorus sits directly below nitrogen in group 15 of the periodic table, the pnictogens. Like nitrogen, it has five valence electrons, but it is much more reactive and is never found as a free element in nature. Phosphorus exists in several forms called allotropes: white phosphorus is highly reactive and catches fire in air, red phosphorus is much more stable, and black phosphorus is the least reactive and conducts electricity. Phosphorus most often bonds with oxygen to form phosphates, which are some of the most important compounds in living things.
Natural Occurrence
Phosphorus makes up about 0.1% of the Earth’s crust, mostly locked up in phosphate rock such as apatite. It is essential for all life: phosphates form the backbone of DNA and RNA, carry energy in cells as ATP, and, as calcium phosphate, make bones and teeth hard. An adult human body contains roughly 0.7 kg of phosphorus. In nature, phosphorus moves slowly through the phosphorus cycle, from rocks into soil, plants and animals, and back into sediments.
Uses
Phosphorus has many important applications:
- Agriculture: Most phosphorus mined today is made into fertilizers, because plants need it to grow roots, flowers and seeds.
- Matches: Red phosphorus is used on the striking strip of safety matchboxes.
- Food and drinks: Phosphoric acid gives cola drinks their tangy taste, and phosphates are used in baking powder.
- Industry: Phosphorus compounds are used to make steel, flame retardants, and water treatment chemicals.
- Electronics: Small amounts of phosphorus are added to silicon to make semiconductors for computer chips and solar cells.
Phosphorus is so vital to life that it is sometimes called a limiting nutrient: too little holds back plant growth, while too much fertilizer washing into lakes causes algal blooms. Managing this precious resource wisely is an important challenge for farming and the environment.