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Chemical element · Atomic number 27
Cobalt (Co)
Transition metals · Period 4 · Solid
Element identity
- Atomic number (Z)
- 27
- Symbol
- Co
- Atomic weight / isotope mass number
- 58.933 194(3)
- Category
- Transition metals
- Physical state (reference)
- Solid
- Period
- 4
- Group (reference)
- 9
- Block
- d
Physical properties
- Appearance
- Hard lustrous gray metal
- Density
- 8.90 g·cm⁻³
- Melting point
- 1768 K / 1495 °C / 2723 °F
- Boiling point
- 3200 K / 2927 °C / 5301 °F
- Sublimation point
- Not available
Atomic and material properties
- Electron configuration
- [Ar] 3d⁷ 4s²
- Electrons per shell
- K2 L8 M15 N2
- Oxidation states
- −3, −1, 1, 2, 3, 4, 5
- Electronegativity (Pauling)
- 1.88
- Atomic radius
- 152 pm
- Covalent radius
- Low spin: 126±3 pm High spin: 150±7 pm
- Molar ionization energies
- 1st: 760.4 kJ·mol⁻¹ 2nd: 1648 kJ·mol⁻¹ 3rd: 3232 kJ·mol⁻¹ 4th: 4950 kJ·mol⁻¹ 5th: 7670 kJ·mol⁻¹ 6th: 9840 kJ·mol⁻¹ 7th: 12,440 kJ·mol⁻¹ 8th: 15,230 kJ·mol⁻¹ 9th: 17,959 kJ·mol⁻¹ 10th: 26,570 kJ·mol⁻¹ 11th: 29,400 kJ·mol⁻¹ 12th: 32,400 kJ·mol⁻¹ 13th: 36,600 kJ·mol⁻¹ 14th: 39,700 kJ·mol⁻¹ 15th: 42,800 kJ·mol⁻¹ 16th: 49,396 kJ·mol⁻¹ 17th: 52,737 kJ·mol⁻¹ 18th: 134,810 kJ·mol⁻¹ 19th: 145,170 kJ·mol⁻¹ 20th: 154,700 kJ·mol⁻¹ 21st: 167,400 kJ·mol⁻¹ 22nd: 178,100 kJ·mol⁻¹ 23rd: 189,300 kJ·mol⁻¹ 24th: 204,500 kJ·mol⁻¹ 25th: 214,100 kJ·mol⁻¹ 26th: 920,870 kJ·mol⁻¹ 27th: 966,023 kJ·mol⁻¹
- Thermal conductivity
- 100 W·m⁻¹·K⁻¹
- Molar heat capacity
- 24.81 J·mol⁻¹·K⁻¹
- Crystal structure
- Hexagonal close packed
- CAS number
- 7440-48-4
Property source: Wikipedia — Cobalt, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.
Sources and interpretation
Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.
Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.
Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.
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