Periodic table › Carbon
1. Identity and classification
Transparent crystalline solid as diamond; soft black-gray hexagonal sheets as graphite
- Name and symbol
- Carbon (Carbon) · C
- Atomic number
- 6
- Relative atomic weight / mass number
- 12.011 ± 0.002
- Group · period · block
- 14 · 2 · p
- Category
- Reactive Nonmetal
- State near room temperature
- Solid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7440-44-0
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
- 6 · 6
- Neutrons in reference isotope
- 6 (12C)
- Full electron configuration
1s² 2s² 2p²- Abbreviated configuration
[He]2s² 2p²- Electrons per shell
- 2, 4
- Listed oxidation states
- +4, +2, -4
- Electronegativity
- 2.55 (Pauling)
- First ionization energy
- 1086.425 kJ/mol · 11.26 eV
- Electron affinity
- 121.861 kJ/mol
- Covalent radius
- 76 pm
- van der Waals radius
- 170 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 2.267 g/cm³
- Melting point
- Not established
- Boiling point
- Not established
- Crystal structure
- Hexagonal
- Specific heat
- 0.709 J/(g·K)
- Thermal conductivity
- 140 W/(m·K)
- Enthalpy of fusion
- 117 kJ/mol
- Enthalpy of vaporization
- 715 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- Not established
Sublimation: 4098 K (solid to gas at 1 atm)
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
Diamond, graphite and graphene have distinct structures and electrical properties.
Selected compounds: CO₂ (Carbon dioxide) · CH₄ (Methane) · CaCO₃ (Calcium carbonate) · C₆H₁₂O₆ (Glucose) · SiC (Silicon carbide)
Reaction reference
Carbon burns to carbon dioxide; limited oxygen can yield carbon monoxide.
No ordinary reaction with cold water; steam can react with hot carbon.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 12C | Stable | 98.94% | Stable |
| 13C | Stable | 1.06% | Stable |
| 14C | Radioactive | — | 5700 Y |
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
- Known since antiquity; no exact discovery year
- Scientists associated with discovery
- Known since antiquity
- Location
- Ancient Egypt & Sumer
- Origin
- Natural
- Listed crustal abundance
- 200 ppm
Minerals and naming reference
Calcite/Limestone (CaCO₃), Dolomite, Coal, Graphite, Diamond, Hydrocarbons
From Latin 'carbo' meaning coal or charcoal
7. Applications
Pencil leads (graphite), diamond jewelry, activated charcoal water filters, baking soda
Detailed applications by field
- everyday
- Pencil leads (graphite), diamond jewelry, activated charcoal water filters, baking soda
- industry
- Steelmaking (coke reducing agent and carbon alloying), carbon black in automobile tires, plastics
- electronics
- Graphene and carbon nanotubes, brushes in electric motors, lithium-ion battery anodes
- medicine
- Activated charcoal for acute toxin adsorption, biocompatible pyrolytic carbon heart valves
- energy
- Graphite neutron moderators in nuclear reactors, fuel cell electrodes, fossil hydrocarbons
- aerospace
- Carbon-fiber-reinforced polymer (CFRP) airframes, heat shields, and rocket nozzles
- agriculture
- Biochar soil amendment, urea nitrogen fertilizers, organic humus cycle
- science
- Radiocarbon dating (¹⁴C), buckminsterfullerene (C₆₀) nanotech research
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
Backbone element of all known terrestrial life—forming stable covalent chains and rings in DNA, RNA, proteins, enzymes, lipids, and carbohydrates.