Element: Chromium
General data
| Element name | Chromium |
|---|---|
| Chemical symbol | Cr |
| Atomic number Z | 24 |
| Year discovered | 1797 |
| Standard state (25°C) | Solid |
| Category | Transition metal |
| Block | d |
| Atomic mass | 51.996 |
| CPK color | #8A99C7 |
Physical properties
| Melting point | 2180 K (1907 °C) |
|---|---|
| Boiling point | 2944 K (2671 °C) |
| Density | 7.15 g/cm³ |
Energy properties
| First ionization energy | 6.767 eV |
|---|---|
| Electron affinity | 0.666 eV |
Atomic structure
| Protons | 24 (Atomic number) |
|---|---|
| Neutrons (Cr-52, most abundant isotope) | 28 |
| Electrons | 24 |
| Electron configuration | [Ar] 3d⁵ 4s¹ |
| Oxidation states | +6, +3, +2 |
| Electronegativity (Pauling) | 1.66 |
| Atomic radius (van der Waals) | 189 pm |
Ionization energies - NIST ASD (24 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Cr I | 0+ | 6.76651 ± 0.00004 | measured |
| Cr II | 1+ | 16.486305 ± 0.000015 | measured |
| Cr III | 2+ | 30.959 ± 0.025 | measured |
| Cr IV | 3+ | 49.16 ± 0.05 | semi-empirical |
| Cr V | 4+ | 69.46 ± 0.04 | semi-empirical |
| Cr VI | 5+ | 90.6349 ± 0.0007 | measured |
| Cr VII | 6+ | 160.29 ± 0.06 | semi-empirical |
| Cr VIII | 7+ | 184.76 ± 0.15 | semi-empirical |
| Cr IX | 8+ | 209.5 ± 0.3 | semi-empirical |
| Cr X | 9+ | 244.5 ± 0.5 | semi-empirical |
| Cr XI | 10+ | 270.8 ± 0.5 | semi-empirical |
| Cr XII | 11+ | 296.7 ± 0.6 | semi-empirical |
| Cr XIII | 12+ | 354.7 ± 0.3 | semi-empirical |
| Cr XIV | 13+ | 384.163 ± 0.006 | semi-empirical |
| Cr XV | 14+ | 1011.6 ± 0.5 | semi-empirical |
| Cr XVI | 15+ | 1097.2 ± 1.4 | semi-empirical |
| Cr XVII | 16+ | 1188 ± 2.1 | semi-empirical |
| Cr XVIII | 17+ | 1294.8 ± 1.6 | semi-empirical |
| Cr XIX | 18+ | 1394.5 ± 0.7 | semi-empirical |
| Cr XX | 19+ | 1495.1 ± 0.7 | semi-empirical |
| Cr XXI | 20+ | 1634.1 ± 0.5 | semi-empirical |
| Cr XXII | 21+ | 1721.183 ± 0.007 | calculated |
| Cr XXIII | 22+ | 7481.8624 ± 0.0012 | calculated |
| Cr XXIV | 23+ | 7894.80289 ± 0.00019 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
Isotopes (29)
| A | N | Half-life | Decay |
|---|---|---|---|
| Cr-42 | 18 | 13.3 ms | EC/β⁺ |
| Cr-43 | 19 | 21.1 ms | EC/β⁺ |
| Cr-44 | 20 | 42.8 ms | EC/β⁺ |
| Cr-45 | 21 | 60.9 ms | EC/β⁺ |
| Cr-46 | 22 | 244.3 ms | EC/β⁺ |
| Cr-47 | 23 | 460.6 ms | EC/β⁺ |
| Cr-48 | 24 | 21.56 h | EC/β⁺ |
| Cr-49 | 25 | 42.3 min | EC/β⁺ |
| Cr-50 | 26 | stable | - |
| Cr-51 | 27 | 27.7004 d | EC |
| Cr-52 | 28 | stable | - |
| Cr-53 | 29 | stable | - |
| Cr-54 | 30 | stable | - |
| Cr-55 | 31 | 3.498 min | β⁻ |
| Cr-56 | 32 | 5.94 min | β⁻ |
| Cr-57 | 33 | 21.1 s | β⁻ |
| Cr-58 | 34 | 7.0 s | β⁻ |
| Cr-59 | 35 | 1.05 s | β⁻ |
| Cr-60 | 36 | 490 ms | β⁻ |
| Cr-61 | 37 | 243 ms | β⁻ |
| Cr-62 | 38 | 206 ms | β⁻ |
| Cr-63 | 39 | 129 ms | β⁻ |
| Cr-64 | 40 | 43 ms | β⁻ |
| Cr-65 | 41 | 28 ms | β⁻ |
| Cr-66 | 42 | 24 ms | β⁻ |
| Cr-67 | 43 | unknown | β⁻ |
| Cr-68 | 44 | unknown | β⁻ |
| Cr-69 | 45 | unknown | β⁻ |
| Cr-70 | 46 | unknown | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce
- Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0