Carbon(C)
Carbon is a reactive nonmetal that forms the backbone of organic chemistry, occurring as graphite, diamond, and in countless compounds.
KEY PROPERTIES
Electron configuration & shells
[He] 2s² 2p²
Shell model is schematic — see lesson on atomic structure for orbitals. Oxidation states: -4, +2, +4. Common ions: C⁴⁺, C⁴⁻.
Measured properties
Values at stated conditions; missing data shown as “—”. Radii distinguished by type; densities at stated phase/temperature.
- Electronegativity (Pauling)
- 2.55
- First ionization energy
- 1086 kJ·mol⁻¹ (first ionization, gas phase)
- Atomic radius
- 67 pm (calculated)
- Covalent radius
- 76 pm (covalent)
- Van der Waals radius
- 170 pm (van der Waals)
- Density
- 2.267 g·cm⁻³ (solid at 20 °C, 1 atm)
- Melting point
- 3915 K (1 atm)
- Boiling point
- 4600 K (1 atm)
Standard conditions: 1 atm unless noted. Values with null are not established or not comparable across allotropes. Radii are distinguished by type. Densities at stated phase/temperature.
| Mass number | Abundance | Stability | Half-life |
|---|---|---|---|
| 12 | 98.93% | stable | — |
| 13 | 1.07% | stable | — |
| 14 | trace/synthetic | radioactive | 5700 y |
Isotopic abundances are natural terrestrial values where applicable; synthetic isotopes shown as trace.
Occurrence & uses
Fourth most abundant in the universe. Ubiquitous in carbonates, fossil fuels, and living matter.
- Steel alloying
- Organic chemistry backbone
- Graphite electrodes
BIOLOGICAL ROLE
Biologically relevant — see uses/occurrence for context.
Discovery
Ancient — known since antiquity — ancient
Safety
Compounds featuring C
Reactions involving C
RELATED CONTENT
SOURCES
- [nist-atomic-weights]nist-atomic-weights (2022)/#nist-atomic-weights
- [nist-2022]nist-2022 (2022)/#nist-2022
- [iupac-gold]iupac-gold (2022)/#iupac-gold
Last reviewed: 2026-08-22 • Reviewer: dr-example