Periodic table › Phosphorus
1. Identity and classification
Non-conducting gas or brittle molecular/network solid
- Name and symbol
- Phosphorus (Phosphorus) · P
- Atomic number
- 15
- Relative atomic weight / mass number
- 30.974 ± 0.001
- Group · period · block
- 15 · 3 · p
- Category
- Reactive Nonmetal
- State near room temperature
- Solid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7723-14-0
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 15 · 15
- Neutrons in reference isotope
- 16 (31P)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p³- Abbreviated configuration
[Ne]3s² 3p³- Electrons per shell
- 2, 8, 5
- Listed oxidation states
- +5, +3, -3
- Electronegativity
- 2.19 (Pauling)
- First ionization energy
- 1011.842 kJ/mol · 10.487 eV
- Electron affinity
- 71.978 kJ/mol
- Covalent radius
- 107 pm
- van der Waals radius
- 180 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 1.82 g/cm³
- Melting point
- 317.3 K · 44.15 °C · 111.47 °F
- Boiling point
- 553.65 K · 280.5 °C · 536.9 °F
- Crystal structure
- Orthorhombic (black phosphorus); other allotropes differ
- Specific heat
- 0.769 J/(g·K)
- Thermal conductivity
- 0.236 W/(m·K)
- Enthalpy of fusion
- 0.66 kJ/mol
- Enthalpy of vaporization
- 12.4 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- 1160 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The listed electron configuration and oxidation states describe atomic structure; compound properties depend on bonding and composition.
Selected compounds: PO / P₂O₃ (Oxide) · PClₙ (Chloride) · PFₙ (Fluoride)
Reaction reference
Oxidation behavior depends on temperature, surface passivation and the chemical environment.
Direct reaction with water is element- and condition-dependent.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 31P | Stable | 100% | Stable |
| 32P | Radioactive | — | 14.268 d |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1669 CE
- Scientists associated with discovery
- Hennig Brand
- Location
- Germany (Hamburg)
- Origin
- Natural
- Listed crustal abundance
- Not established
Minerals and naming reference
Apatite / Phosphate rock (Ca₅(PO₄)₃(F,Cl,OH))
Named from scientific/historical roots associated with Phosphorus (P), discovered or characterized by Hennig Brand.
7. Applications
DNA/RNA & ATP backbone, agricultural NPK fertilizers, safety match striking surfaces, LFP battery cathodes
Detailed applications by field
- everyday
- DNA/RNA & ATP backbone, agricultural NPK fertilizers, safety match striking surfaces, LFP battery cathodes
- industry
- Used in reactive nonmetal processing, specialized alloys, and chemical manufacturing (DNA/RNA & ATP backbone, agricultural NPK fertilizers, safety match striking surfaces, LFP battery cathodes).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Phosphorus's electronic structure ([Ne] 3s² 3p³) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Phosphorus.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Phosphorus.
- agriculture
- Soil geochemistry analysis, trace micronutrient research, or analytical environmental monitoring.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 3 p-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as essential in human and biological systems.