Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram (compare copper at about 0.06 grams). In minerals, phosphorus generally occurs as phosphate.

Phosphorus, 15P
waxy white (yellow cut), red (granules centre left, chunk centre right), and violet phosphorus
Pronunciation/ˈfɒsfərəs/ (FOS-fər-əs)
Appearancewaxy white, yellow, red, violet, black metallic-looking
Standard atomic weight Ar, std(P)30.973761998(5)[1]
in the Earth's crust5.2 (silicon = 100)
Phosphorus in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)15
Groupgroup 15 (pnictogens)
Periodperiod 3
Block  p-block
Electron configuration[Ne] 3s2 3p3
Electrons per shell2, 8, 5
Physical properties
Phase at STPsolid
Melting pointwhite: 317.3 K (44.15 °C, 111.5 °F)
red: 860 K (590 °C, 1090 °F)[2]
Boiling pointwhite: 553.7 K (280.5 °C, 536.9 °F)
Sublimation pointred: ≈689.2–863 K (≈416–590 °C, ≈780.8–1094 °F)
violet: 893 K (620 °C, 1148 °F)
Density (near r.t.)white: 1.823 g/cm3
red: ≈2.2–2.34 g/cm3
violet: 2.36 g/cm3
black: 2.69 g/cm3
Heat of fusionwhite: 0.66 kJ/mol
Heat of vaporisationwhite: 51.9 kJ/mol
Molar heat capacitywhite: 23.824 J/(mol·K)
Vapour pressure (white)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 279 307 342 388 453 549
Vapour pressure (red, b.p. 431 °C)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 455 489 529 576 635 704
Atomic properties
Oxidation states−3, −2, −1, 0,[3] +1,[4] +2, +3, +4, +5 (a mildly acidic oxide)
ElectronegativityPauling scale: 2.19
Ionisation energies
  • 1st: 1011.8 kJ/mol
  • 2nd: 1907 kJ/mol
  • 3rd: 2914.1 kJ/mol
  • (more)
Covalent radius107±3 pm
Van der Waals radius180 pm
Color lines in a spectral range
Spectral lines of phosphorus
Other properties
Natural occurrenceprimordial
Crystal structure body-centred cubic (bcc)
Thermal conductivitywhite: 0.236 W/(m⋅K)
black: 12.1 W/(m⋅K)
Magnetic orderingwhite, red, violet, black: diamagnetic[5]
Molar magnetic susceptibility−20.8×10−6 cm3/mol (293 K)[6]
Bulk moduluswhite: 5 GPa
red: 11 GPa
CAS Number7723-14-0 (red)
12185-10-3 (white)
DiscoveryHennig Brand (1669)
Recognised as an element byAntoine Lavoisier[7] (1777)
Main isotopes of phosphorus
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
31P 100% stable
32P trace 14.28 d β 32S
33P trace 25.3 d β 33S
 Category: Phosphorus
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Elemental phosphorus was first isolated as white phosphorus in 1669. White phosphorus emits a faint glow when exposed to oxygen – hence the name, taken from Greek mythology, Φωσφόρος meaning "light-bearer" (Latin Lucifer), referring to the "Morning Star", the planet Venus. The term "phosphorescence", meaning glow after illumination, derives from this property of phosphorus, although the word has since been used for a different physical process that produces a glow. The glow of phosphorus is caused by oxidation of the white (but not red) phosphorus — a process now called chemiluminescence. Together with nitrogen, arsenic, antimony, and bismuth, phosphorus is classified as a pnictogen.

Phosphorus is an element essential to sustaining life largely through phosphates, compounds containing the phosphate ion, PO43−. Phosphates are a component of DNA, RNA, ATP, and phospholipids, complex compounds fundamental to cells. Elemental phosphorus was first isolated from human urine, and bone ash was an important early phosphate source. Phosphate mines contain fossils because phosphate is present in the fossilized deposits of animal remains and excreta. Low phosphate levels are an important limit to growth in some aquatic systems. The vast majority of phosphorus compounds mined are consumed as fertilisers. Phosphate is needed to replace the phosphorus that plants remove from the soil, and its annual demand is rising nearly twice as fast as the growth of the human population. Other applications include organophosphorus compounds in detergents, pesticides, and nerve agents.