← Periodic table · Nonmetals

Phosphorus (P)

Phosphorus (symbol P) is the chemical element with atomic number 15: a nonmetal, solid at 0 °C, with an atomic mass of 30.974 u. Discovered in 1669 (Hennig Brand).

Phosphorus is the first element whose discoverer we know: an alchemist looking for gold in urine. Its white form glows in the dark and bursts into flame spontaneously in air. It is a pillar of life: it links the building blocks of DNA, stores energy in ATP and hardens our bones. Its economically recoverable reserves, concentrated in a handful of countries, are crucial to world agriculture.

Key facts

Atomic number
15
Symbol
P
French name
Phosphore
Atomic mass
30.974 u
Molar mass
30.974 g/mol
Family
Nonmetals
Position
period 3, group 15, p-block
State at 0 °C
Solid
Melting point
44.2 °C
Boiling point
280.6 °C
Density
1.82 g/cm³
Electronegativity (Pauling)
2.19
First ionization energy
1,012 kJ/mol
Atomic radius
100 pm
Electron configuration
[Ne] 3s² 3p³
Abundance in Earth's crust
1,050 ppm (11th most abundant element)
Indicative price
3 $/kg (order of magnitude)
Radioactive
no
Discovery
1669, Hennig Brand

Origin of the name

From the Greek phōsphoros, “light-bearer.”

What does phosphorus look like?

Several forms: white phosphorus, waxy and translucent, which glows in the dark; red phosphorus, a stable powder; black phosphorus, flaky like graphite.

Where is phosphorus found?

About 0.1% of Earth's crust, always as phosphates. The large deposits are ancient marine sediments. The human body contains about 700 g, 85% of it in bones and teeth.

Natural sources

  • Apatite (fluorapatite)
  • Phosphorite (phosphate rock)
  • Guano

How is phosphorus produced?

About 220 million tonnes of phosphate rock are mined each year and treated with sulfuric acid to make phosphoric acid and fertilizers. Elemental phosphorus is obtained by heating the rock with coke and silica in an electric furnace. Morocco holds about 70% of world reserves.

Top producers

  • China
  • Morocco
  • United States
  • Russia

What is phosphorus used for?

  • Phosphate fertilizers (about 80% of consumption).
  • Food additives (phosphoric acid in colas, baking powder).
  • The striking strip on matchboxes (red phosphorus).
  • Flame retardants and metal surface treatment.
  • Lithium iron phosphate (LFP) batteries.

In everyday life

  • The striking strip on a matchbox
  • Cola drinks
  • NPK garden fertilizers
  • The battery in some electric cars

Role in living things

Essential: phosphates form the backbone of DNA and RNA, ATP stores the cell's energy, and phospholipids make up cell membranes. Bone is largely made of hydroxyapatite, a calcium phosphate.

Hazards of phosphorus

White phosphorus is highly toxic and ignites spontaneously at around 30 °C; it has been used as an incendiary weapon. In the 19th century, women working in match factories suffered from “phossy jaw,” a necrosis of the jawbone. Some organophosphorus compounds are pesticides or nerve agents (sarin). Phosphate runoff triggers algal blooms in rivers.

Cosmic origin

  • Supernovae: Forged in the cores of massive stars, then scattered when they explode.

History of phosphorus

In 1669 in Hamburg, the alchemist Hennig Brand boiled down buckets of urine in hopes of making the philosopher's stone. He obtained a substance that glowed in the dark and named it phosphorus, Greek for “light-bearer.” It took a century to realize that bones are a better source.

Did you know?

  • Using Brand's method, it took hundreds of liters of urine to obtain a few grams of phosphorus.
  • The glow of white phosphorus is not phosphorescence but a slow reaction with oxygen in the air (chemiluminescence).
  • Safety matches keep the reactants apart: the red phosphorus is on the striking strip, not on the match head.

Isotopes of phosphorus

A single stable isotope, phosphorus-31. Radioactive phosphorus-32 was one of the very first tracers in molecular biology.

  • phosphorus-31: 100% of natural phosphorus, stable. A workhorse of NMR for studying ATP and energy metabolism.
  • phosphorus-32: radioactive, half-life 14.3 days. DNA label in biology and a treatment for certain blood disorders.
  • phosphorus-33: radioactive, half-life 25.4 days. A gentler tracer than phosphorus-32 for labeling DNA.

Common compounds

Hydroxyapatite (Ca₅(PO₄)₃(OH)) · Lithium iron phosphate (LiFePO₄)

Related elements

Same family (nonmetals): Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Sulfur (S), Selenium (Se).

Same column (group 15): Nitrogen (N), Arsenic (As), Antimony (Sb), Bismuth (Bi), Moscovium (Mc).