Chromium (Cr)
Chromium is element 24, a transition metal in period 4, group 6 of the periodic table. At room temperature it is a solid.
Electron configuration [Ar] 3d5 4s1
Electrons per shell 2, 8, 13, 1
Chromium data
| Atomic number | 24 |
|---|---|
| Symbol | Cr |
| Atomic mass | 51.996 u |
| Category | Transition metal |
| Group | 6 |
| Period | 4 |
| Block | d |
| State at 25 °C | solid |
| Melting point | 2180 K (1906.9 °C) |
| Boiling point | 2944 K (2670.9 °C) |
| Density | 7.14 g/cm³ |
| Electronegativity (Pauling) | 1.66 |
| Atomic radius | 127 pm |
| 1st ionization energy | 653 kJ/mol |
| Electron affinity | -64 kJ/mol |
| Oxidation states | -2, -1, +1, +2, +3, +4, +5, +6 |
| Common ion charge | 3+, 6+ |
| Discovered | Known since antiquity |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through chromium’s configuration and its ions →
Where chromium sits
Chromium belongs to the transition metals. Its Pauling electronegativity of 1.66 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Chromium FAQ
What is the electron configuration of chromium?
Chromium (Z = 24) has the configuration 1s2 2s2 2p6 3s2 3p6 3d5 4s1. In noble-gas shorthand that is [Ar] 3d5 4s1. This is an exception to the simple Aufbau prediction (1s2 2s2 2p6 3s2 3p6 3d4 4s2); a half-filled or filled subshell lowers the energy.
How many valence electrons does chromium have?
6 (1 outer s + 5 d electrons; 1 in the outermost shell).
What is the atomic mass of chromium?
The standard atomic weight of chromium is 51.996 u, so one mole weighs 51.996 g.
Is chromium a metal?
Yes. Chromium is a transition metal.
What is the charge of a chromium ion?
Chromium most commonly forms Cr3+ or Cr6+.