Carbon
polyatomic nonmetal · period 2 · group 14 · p-block
Carbon (from Latin: carbo "coal") is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.
What the numbers say
At standard temperature and pressure Carbon is a solid, sitting in period 2, group 14 of the p-block.
Its melting point of 3823 K (3550 °C) is the 1st highest of the 110 elements with a measured value — one of the most refractory elements there is.
At 2.26 g/cm³ it is the 75th densest of 96 elements with a quoted density.
Pauling electronegativity is 2.55. Paired with oxygen (3.44) that is a difference of 0.89, which puts the bond polar covalent — oxides here tend to be semiconducting or refractory rather than salt-like.
In the solid state it takes a simple hexagonal structure — hexagonal packing offers few easy slip systems, so properties are anisotropic and formability is limited.
It is reported in 8 oxidation states (-4, -3, -2, -1, 1, 2, 3, 4), which sets how many distinct compounds and phases it can form.
First identified in c. 3750 BCE.
Crystal structure
Solid Carbon adopts a Simple Hexagonal arrangement, in the Hexagonal system — axes a = b ≠ c, angles α = β = 90°, γ = 120°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Where carbon shows up in engineering materials
3 entries in the materials library name it directly:
- AISI 1045 carbon steel — Medium-carbon steel
- AISI 316L / 1.4404 stainless — Austenitic stainless
- CFRP (carbon/epoxy laminate) — Polymer-matrix composite
Crystallographic examples
Carbon or one of its compounds is a textbook example for this crystal system:
- Orthorhombic — α-S, cementite Fe₃C, aragonite CaCO₃, olivine
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing C — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 4
Properties
| Atomic number | 6 |
|---|---|
| Atomic mass | 12.011 u |
| Series | polyatomic nonmetal |
| Group | 14 |
| Period | 2 |
| Block | p-block |
| Phase at STP | Solid |
| Density | 2.26 g/cm³ |
| Melting point | 3823 K (3550 °C) |
| Boiling point | 4300 K (4027 °C) |
| Electronegativity (Pauling) | 2.55 |
| Electron configuration | [He] 2s² 2p² |
| Crystal structure | Simple Hexagonal |
| Oxidation states | -4,-3,-2,-1,1,2,3,4 |
| Discovered | c. 3750 BCE |
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See C in context with all 118 elements.
Working with carbon in a real design?
Ask the materials chat how C behaves in your alloy system, what it does to weldability, and which grades to look at — with the source of every number named.