Chromium
transition metal · period 4 · group 6 · d-block
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6.
What the numbers say
At standard temperature and pressure Chromium is a solid, sitting in period 4, group 6 of the d-block.
Its melting point of 2180 K (1907 °C) is the 16th highest of the 110 elements with a measured value — mid-range among the elements.
At 7.19 g/cm³ it is the 48th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.66. Paired with oxygen (3.44) that is a difference of 1.78, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a body-centered cubic structure — BCC packing is stronger but shows a ductile-to-brittle transition as temperature drops.
It is reported in 8 oxidation states (-2, -1, 1, 2, 3, 4, 5, 6), which sets how many distinct compounds and phases it can form.
First identified in 1797.
Crystal structure
Solid Chromium adopts a Body-centered Cubic arrangement, in the Cubic (isometric) system — axes a = b = c, angles α = β = γ = 90°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Cr — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 13 · N 1
Properties
| Atomic number | 24 |
|---|---|
| Atomic mass | 51.99616 u |
| Series | transition metal |
| Group | 6 |
| Period | 4 |
| Block | d-block |
| Phase at STP | Solid |
| Density | 7.19 g/cm³ |
| Melting point | 2180 K (1907 °C) |
| Boiling point | 2944 K (2671 °C) |
| Electronegativity (Pauling) | 1.66 |
| Electron configuration | [Ar] 3d⁵ 4s¹ |
| Crystal structure | Body-centered Cubic |
| Oxidation states | -2,-1,1,2,3,4,5,6 |
| Discovered | 1797 |
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See Cr in context with all 118 elements.
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