2758.933CoCobalt
Cobalt (Co) — element 27transition metal · group 9, period 4
Cobalt is a chemical element with the symbol Co and atomic number 27. It is a transition metal in group 9, period 4 of the periodic table (the d-block), with a standard atomic mass of 58.933 u. At room temperature (25 °C) cobalt is a solid.
💡 Known for: Used in lithium-ion battery cathodes, jet-engine superalloys and deep blue pigments; it is part of vitamin B12.
# Cobalt properties
| Symbol | Co |
|---|---|
| Atomic number | 27 |
| Atomic mass | 58.933 u |
| Category | transition metal |
| Group | 9 |
| Period | 4 |
| Block | d-block |
| Electron configuration | [Ar] 3d⁷ 4s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s² |
| Electrons per shell | 2, 8, 15, 2 |
| Protons / electrons | 27 / 27 |
| State at 25 °C | solid |
| Melting point | 1768 K (1494.8 °C, 2722.7 °F) |
| Boiling point | 3200 K (2926.8 °C, 5300.3 °F) |
| Density | 8.9 g/cm³ |
| Electronegativity (Pauling) | 1.88 |
| First ionization energy | 7.881 eV |
| Atomic radius | 152 pm |
| Discovered | 1735 |
# Electron configuration of cobalt
The electron configuration of cobalt is [Ar] 3d⁷ 4s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s². Its 27 electrons fill 4 shells as 2, 8, 15, 2, so the outermost shell holds 2 electrons.
# Related elements
FeIronprevious elementNiNickelnext elementRhRhodiumgroup 9IrIridiumgroup 9MtMeitneriumgroup 9ScScandiumtransition metalTiTitaniumtransition metalVVanadiumtransition metalCrChromiumtransition metalMnManganesetransition metalCuCoppertransition metalZnZinctransition metalYYttriumtransition metal
# Cobalt FAQ
What is the atomic number of cobalt?
The atomic number of cobalt is 27: every cobalt atom has 27 protons in its nucleus. Its symbol is Co.
What is the atomic mass of cobalt?
The standard atomic mass of cobalt is 58.933 u.
What is the electron configuration of cobalt?
Cobalt's electron configuration is [Ar] 3d⁷ 4s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²), with 2, 8, 15, 2 electrons per shell.
Is cobalt a metal?
Yes. Cobalt is a transition metal, one of the metals.
What is the melting point of cobalt?
Cobalt melts at 1768 K (1494.8 °C, 2722.7 °F) and boils at 3200 K (2926.8 °C, 5300.3 °F).
What is cobalt used for / known for?
Used in lithium-ion battery cathodes, jet-engine superalloys and deep blue pigments; it is part of vitamin B12.