Element: Cobalt
General data
| Element name | Cobalt |
|---|---|
| Chemical symbol | Co |
| Atomic number Z | 27 |
| Year discovered | 1735 |
| Standard state (25°C) | Solid |
| Category | Transition metal |
| Block | d |
| Atomic mass | 58.933 |
| CPK color | #F090A0 |
Physical properties
| Melting point | 1768 K (1495 °C) |
|---|---|
| Boiling point | 3200 K (2927 °C) |
| Density | 8.86 g/cm³ |
Energy properties
| First ionization energy | 7.881 eV |
|---|---|
| Electron affinity | 0.661 eV |
Atomic structure
| Protons | 27 (Atomic number) |
|---|---|
| Neutrons (Co-59, most abundant isotope) | 32 |
| Electrons | 27 |
| Electron configuration | [Ar] 4s² 3d⁷ |
| Oxidation states | +3, +2 |
| Electronegativity (Pauling) | 1.88 |
| Atomic radius (van der Waals) | 192 pm |
Ionization energies - NIST ASD (27 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Co I | 0+ | 7.88101 ± 0.00012 | measured |
| Co II | 1+ | 17.0844 ± 0.0012 | measured |
| Co III | 2+ | 33.5 ± 0.06 | semi-empirical |
| Co IV | 3+ | 51.27 ± 0.1 | semi-empirical |
| Co V | 4+ | 79.5 ± 0.2 | semi-empirical |
| Co VI | 5+ | 102 ± 0.2 | semi-empirical |
| Co VII | 6+ | 128.9 ± 0.5 | semi-empirical |
| Co VIII | 7+ | 157.8 ± 0.6 | semi-empirical |
| Co IX | 8+ | 186.14 ± 0.25 | measured |
| Co X | 9+ | 275.4 ± 0.4 | semi-empirical |
| Co XI | 10+ | 305.32 ± 0.23 | semi-empirical |
| Co XII | 11+ | 336.1 ± 0.4 | semi-empirical |
| Co XIII | 12+ | 378.5 ± 0.7 | semi-empirical |
| Co XIV | 13+ | 410 ± 1 | semi-empirical |
| Co XV | 14+ | 441.1 ± 1.4 | semi-empirical |
| Co XVI | 15+ | 511.96 ± 0.06 | semi-empirical |
| Co XVII | 16+ | 546.588 ± 0.015 | semi-empirical |
| Co XVIII | 17+ | 1397.2 ± 0.5 | measured |
| Co XIX | 18+ | 1504.5 ± 1.2 | measured |
| Co XX | 19+ | 1606 ± 4 | semi-empirical |
| Co XXI | 20+ | 1724 ± 3 | semi-empirical |
| Co XXII | 21+ | 1844 ± 1.1 | semi-empirical |
| Co XXIII | 22+ | 1960.8 ± 0.8 | semi-empirical |
| Co XXIV | 23+ | 2119.4 ± 1.9 | semi-empirical |
| Co XXV | 24+ | 2218.876 ± 0.007 | calculated |
| Co XXVI | 25+ | 9544.1817 ± 0.001 | calculated |
| Co XXVII | 26+ | 10012.1297 ± 0.0004 | 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 |
|---|---|---|---|
| Co-50 | 23 | 38.8 ms | EC/β⁺ |
| Co-51 | 24 | 68.8 ms | EC/β⁺ |
| Co-52 | 25 | 111 ms | EC/β⁺ |
| Co-53 | 26 | 244 ms | EC/β⁺ |
| Co-54 | 27 | 193.27 ms | EC/β⁺ |
| Co-55 | 28 | 17.53 h | EC/β⁺ |
| Co-56 | 29 | 77.24 d | EC/β⁺ |
| Co-57 | 30 | 271.80 d | EC |
| Co-58 | 31 | 70.883 d | EC/β⁺ |
| Co-59 | 32 | stable | - |
| Co-60 | 33 | 5.2711 a | β⁻ |
| Co-61 | 34 | 1.650 h | β⁻ |
| Co-62 | 35 | 1.51 min | β⁻ |
| Co-63 | 36 | 26.9 s | β⁻ |
| Co-64 | 37 | 300 ms | β⁻ |
| Co-65 | 38 | 1.16 s | β⁻ |
| Co-66 | 39 | 200 ms | β⁻ |
| Co-67 | 40 | 330 ms | β⁻ |
| Co-68 | 41 | 220 ms | β⁻ |
| Co-69 | 42 | 210 ms | β⁻ |
| Co-70 | 43 | 114 ms | β⁻ |
| Co-71 | 44 | 80 ms | β⁻ |
| Co-72 | 45 | 51.9 ms | β⁻ |
| Co-73 | 46 | 42.0 ms | β⁻ |
| Co-74 | 47 | 31.3 ms | β⁻ |
| Co-75 | 48 | 26.5 ms | β⁻ |
| Co-76 | 49 | 16 ms | β⁻ |
| Co-77 | 50 | 13 ms | β⁻ |
| Co-78 | 51 | 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