Chromium (Cr): Electron Configuration, Properties and Uses
Chromium (Cr): Electron Configuration, Properties and Uses
Electron configuration [Ar] 4s1 3d5 · group 6 · period 4 · Ar 51.996
Chromium data
- Atomic number
- 24
- Relative atomic mass
- 51.996
- Group
- 6
- Period
- 4
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Ar] 4s1 3d5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s1 3d5
- Electrons per shell
- 2, 8, 13, 1 (K L M N)
- Valence electrons
- 6
- Electronegativity (Pauling)
- 1.66
- First ionisation energy
- 6.767 eV
- Atomic radius (van der Waals)
- 189 pm
- State at room temperature
- Solid
- Melting point
- 1907 °C
- Boiling point
- 2671 °C
- Density
- 7.15 g/cm³
- Common oxidation states
- +6, +3, +2
- Discovered
- 1797
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 13 · N 1
Orbital diagram (outer electrons)
About chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is a transition metal in group 6, period 4, d-block. Chromium was first discovered in 1797. Chromium is a solid at room temperature, melting at 1907 °C and boiling at 2671 °C.
Chromium electron configuration
The electron configuration of chromium is 1s2 2s2 2p6 3s2 3p6 4s1 3d5, or in short [Ar] 4s1 3d5. Its electrons occupy 4 shells: K = 2, L = 8, M = 13, N = 1. For transition metals, valence electrons are counted from the 4s and 3d subshells: 1 + 5 = 6, matching group 6. This is an exception to the Aufbau rule: the usual filling order predicts [Ar] 4s2 3d4, but a half-full 3d subshell is more stable, so an electron moves from the s subshell into 3d. When it forms cations, electrons leave the outermost subshell first: Cr2+ = [Ar] 3d4; Cr3+ = [Ar] 3d3.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s1(19) → 3d5(24)
Uses of chromium
The main uses of chromium include chrome plating, stainless steel, pigments and leather tanning. For research and analysis you can browse chromium compounds in the AMI Scientific catalogue.
Safety
Chromium metal is fairly safe, but chromium(VI) compounds such as potassium dichromate are carcinogenic and must be handled in a fume hood. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 6
Frequently asked questions
What is the electron configuration of chromium?
The electron configuration of chromium (Cr, atomic number 24) is 1s2 2s2 2p6 3s2 3p6 4s1 3d5, or [Ar] 4s1 3d5 in short. By shell: 2, 8, 13, 1.
How many valence electrons does chromium have?
Chromium has 6 valence electrons.
Which group and period is chromium in?
Chromium is in group 6, period 4, d-block.
What is the atomic mass of chromium?
The relative atomic mass of chromium is 51.996. Use it to calculate molar mass with the molar mass calculator.
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