Carbon
Element 6 · Nonmetal
Carbon is the element that makes chemistry come alive. With four valence electrons it bonds to itself in endless chains, rings, and sheets, giving rise to diamonds, graphite, graphene, and the millions of organic compounds that build living things. Plants pull carbon dioxide from the air, animals return it by breathing, and the slow carbon cycle moves it through rocks, oceans, and fossil fuels. Industry depends on carbon too: as coke in steelmaking, graphite in batteries and pencils, activated carbon in filters, and carbon fiber in aircraft. No other element comes close to carbon's variety.
Key facts
| Atomic number | 6 |
|---|---|
| Atomic weight | 12.011 |
| Category | Nonmetal |
| Group / Period | 14 / 2 |
| Block | p |
| Electron configuration | 1s2 2s2 2p2 |
| Common oxidation states | +4, +2, -4 |
| State at STP | Solid |
| Electronegativity | 2.55 |
| Atomic radius | 67 pm |
| Density | 2.267 g/cm³ |
| Melting point | 3550 °C (sublimes) |
| Boiling point | 4027 °C (sublimes) |
Occurrence
Carbon dioxide makes up about 0.04 percent of air; far larger stores sit in limestone, fossil fuels, and the oceans. Living biomass and soils hold enormous amounts, cycling constantly between organisms and the atmosphere.
Applications
Steel production (as coke and alloying element)
Graphite electrodes and batteries
Diamond cutting tools and jewelry
Activated carbon filtration
Carbon fiber composites
Polymers and plastics
Common compounds
- Carbon dioxide (CO2)
- Methane (CH4)
- Glucose (C6H12O6)
- Calcium carbonate (CaCO3)
- Carbon monoxide (CO)
Diamond and graphite are both 100 percent carbon. Their opposite properties — hardest gem versus soft pencil lead — come only from how the atoms are stacked.
Data source: IUPAC standard atomic weights 2021