Phosphorus
Phosphorus is a reactive nonmetal that exists in several strikingly different forms, from the pale, glowing, dangerously flammable white variety to the much more stable red form used in matches. It's also essential to life, forming part of the backbone of DNA and RNA and of ATP, the molecule every cell uses to store and transfer energy.
- Group · Period
- 15 · 3
- At room temp
- solid
- Melts at
- 317.3 K
- Density
- 1.82 g/cm³
- Discovered
- 1669
Uses
Phosphorus compounds are essential to modern agriculture: phosphate fertilizers supply plants with a nutrient they need in large quantities, making phosphorus mining and processing a cornerstone of the global food supply. Red phosphorus, a more stable form of the element, is used in the striking surface on matchboxes, while phosphorus compounds also appear in some flame retardants and in steel and detergent manufacturing.
Biologically, phosphorus is irreplaceable — phosphate groups form part of the backbone of DNA and RNA, and phosphorus is a core component of ATP, the molecule that powers cellular processes throughout the body. Phosphorus compounds are also a major component of tooth enamel and bone, alongside calcium.
History
Phosphorus was discovered in 1669 by German alchemist Hennig Brand, who was attempting to extract gold from human urine and instead isolated a strange, glowing substance. This makes him the first person in recorded history credited by name with discovering a chemical element — everything known before it had no single identifiable discoverer. Brand initially kept his method secret, but knowledge of it spread among other chemists over the following years. Its name comes from the Greek for “light-bearer,” a reference to the faint glow given off by white phosphorus.
Fun facts
- Phosphorus was the first element in history to be discovered by a known individual — every element known before it, like gold, carbon, and sulfur, had no single credited discoverer.
- White phosphorus glows faintly in the dark through a chemical reaction with air, which is exactly where its name — Greek for 'light-bearer' — comes from.
- Phosphorus is essential to life, forming part of the structural backbone of DNA and RNA and of ATP, the molecule cells use to store and transfer energy.
Frequently asked questions
Is it true phosphorus was discovered while someone was looking for gold in urine?
Yes. German alchemist Hennig Brand was trying to extract gold from large quantities of boiled-down human urine, reasoning that its golden color might hold a clue. Instead, he isolated a glowing, waxy new substance — phosphorus — as an unexpected byproduct of the process.
Why is phosphorus stored underwater?
That applies specifically to white phosphorus, which is highly reactive and ignites spontaneously when exposed to air. Storing it submerged in water keeps oxygen away from it, preventing it from catching fire on its own.
Is all phosphorus dangerous to be around?
No — white phosphorus is toxic and highly flammable, but other forms are much safer. Red phosphorus, used in the striking strips on matchboxes, is far more stable, and the phosphorus compounds in fertilizers and in your own body's DNA and bones are completely different from the hazardous elemental white form.
Compounds
6 notable compounds containing P
- Ca3(PO4)2mineral
Calcium phosphate
An ionic salt that, in its hydroxyapatite form, makes up the mineral structure of bones and teeth.
Used for: Fertilizer, dietary supplement, food additive
- InPsemiconductor
Indium phosphide
A III-V semiconductor with a direct bandgap well suited to generating and carrying light, making it central to modern fiber-optic technology.
Used for: High-speed fiber-optic transceivers and laser diodes
- H3PO4acid
Phosphoric acid
A triprotic acid built around a central phosphorus atom bonded to four oxygens, moderately strong and notably non-volatile.
Used for: Soft drink acidity/flavoring, fertilizer production, rust removal
- P4O10oxide
Phosphorus pentoxide
A molecular oxide built from four phosphorus atoms linked through oxygen bridges into a cage-like structure, and one of the most powerful common drying agents.
Used for: Dehydrating agent, precursor to phosphoric acid
- Na3PO4salt
Sodium phosphate
An alkaline ionic salt of phosphoric acid, sold as trisodium phosphate for its strong grease-cutting cleaning power.
Used for: Heavy-duty cleaning agent, food additive, water treatment
- RhCl(PPh3)3reagent
Wilkinson's catalyst
A landmark rhodium complex bearing three triphenylphosphine ligands that catalyzes the hydrogenation of alkenes under mild conditions, a discovery that helped found modern homogeneous catalysis.
Used for: Homogeneous catalyst for hydrogenating alkenes in organic synthesis
Isotopes
22 known isotopes
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| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| P-31 stable | 100% | Stable | — | -24,440.54 keV | 8,481.17 keV | — |
Show all 22 isotopes
| P-25 | — | 30 ns | Proton emission (100%) | 20,190 keV | 6,794 keV | 1.52 × 10-8 eV |
| P-26 | — | 43.7 ms | Electron capture / beta-plus decay (100%), ECP (36.8%), EC2P (2.16%) | 10,973 keV | 7,198 keV | 1.04 × 10-14 eV |
| P-27 | — | 260 ms | Electron capture / beta-plus decay (100%), Beta-plus, proton emission (0.07%) | -659.03 keV | 7,661.09 keV | 1.75 × 10-15 eV |
| P-28 | — | 270.3 ms | Electron capture / beta-plus decay (100%), ECP (0.0013%), ECA (0.00086%) | -7,147.86 keV | 7,907.48 keV | 1.69 × 10-15 eV |
| P-29 | — | 4.142 s | Electron capture / beta-plus decay (100%) | -16,952.85 keV | 8,251.24 keV | 1.10 × 10-16 eV |
| P-30 | — | 2.498 m | Electron capture / beta-plus decay (100%) | -20,200.86 keV | 8,353.51 keV | 3.04 × 10-18 eV |
| P-32 | — | 14.268 d | Beta-minus decay (100%) | -24,304.88 keV | 8,464.12 keV | 3.70 × 10-22 eV |
| P-33 | — | 25.35 d | Beta-minus decay (100%) | -26,337.35 keV | 8,513.81 keV | 2.08 × 10-22 eV |
| P-34 | — | 12.43 s | Beta-minus decay (100%) | -24,548.7 keV | 8,448.19 keV | 3.67 × 10-17 eV |
| P-35 | — | 47.3 s | Beta-minus decay (100%) | -24,857.81 keV | 8,446.25 keV | 9.65 × 10-18 eV |
| P-36 | — | 5.6 s | Beta-minus decay (100%) | -20,251.05 keV | 8,307.87 keV | 8.15 × 10-17 eV |
| P-37 | — | 2.31 s | Beta-minus decay (100%) | -18,996.01 keV | 8,267.56 keV | 1.98 × 10-16 eV |
| P-38 | — | 0.64 s | Beta-minus decay (100%), Beta-minus, neutron emission (12%) | -14,621.57 keV | 8,147.27 keV | 7.13 × 10-16 eV |
| P-39 | — | 0.28 s | Beta-minus decay (100%), Beta-minus, neutron emission (26%) | -12,774.64 keV | 8,097.97 keV | 1.63 × 10-15 eV |
| P-40 | — | 150 ms | Beta-minus decay (100%), Beta-minus, neutron emission (15.8%), B-2N | -8,139.19 keV | 7,981.42 keV | 3.04 × 10-15 eV |
| P-41 | — | 101 ms | Beta-minus decay (100%), Beta-minus, neutron emission (30%) | -4,979.77 keV | 7,906.55 keV | 4.52 × 10-15 eV |
| P-42 | — | 48.5 ms | Beta-minus decay (100%), Beta-minus, neutron emission (50%), B-2N | 1,091.84 keV | 7,765.91 keV | 9.41 × 10-15 eV |
| P-43 | — | 36.5 ms | Beta-minus decay (100%), Beta-minus, neutron emission (100%), B-2N | 5,040 keV | 7,681 keV | 1.25 × 10-14 eV |
| P-44 | — | 18.5 ms | Beta-minus decay, Beta-minus, neutron emission | 11,110 keV | 7,552 keV | 2.47 × 10-14 eV |
| P-45 | — | 200 ns | Beta-minus decay | 15,960 keV | 7,456 keV | 2.28 × 10-9 eV |
| P-46 | — | — | Beta-minus decay (100%) | 22,840 keV | 7,320 keV | — |