Periodic table / Transition metals
27Cobalt
Cobalt is a transition metal in group 9, period 4. At 25 °C it is a solid.
- Symbol
- Co
- Atomic number
- 27 protons in the nucleus
- Standard atomic weight
- 58.933 ± 0.001
- Electron configuration
- [Ar] 3d7 4s2
- Electrons in each shell
- 2, 8, 15, 2
- Group, period, block
- 9, 4, d
- Family
- Transition metals
- State at 25 °C
- solid
- Electronegativity
- 1.88 (Pauling scale)
- First ionisation energy
- 760.4 kJ/mol (7.88101 eV)
Where these numbers come from
Atomic weight: IUPAC CIAAW, abridged standard atomic weights 2024. Electron configuration and ionisation energy: NIST Atomic Spectra Database. Family, state and electronegativity: PubChem. See Sources. Melting points, boiling points and densities are left out for now: published values differ between sources, and we will add them once each has been checked.