Transition metals
Cobalt
A magnetic metal prized for blue pigments and batteries.
Atomic #27Mass58.933Blockd-blockPeriod4Group9
Co27 · 58.933
3D Atom Explorer
Inside the Cobalt atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Cobalt atom step by step.
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Electron configuration
[Ar] 3d7 4s2
A neutral Cobalt atom has 27 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Shell 12 e⁻Shell 28 e⁻Shell 315 e⁻Shell 42 e⁻
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Properties
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 1768 K (1495 °C)
- Boiling point
- 3200 K (2927 °C)
- Density
- 8.86 g/cm³
- Electronegativity
- 1.88 Pauling
- Atomic radius
- 135 pm
- 1st ionization energy
- 760 kJ/mol
- Category
- Transition metals
History
Discovery & naming
- Discovered
- 1735
- Discovered by
- Georg Brandt
- Origin of name
- German 'kobold', a goblin.
Notable uses
Batteries, powerful magnets, and blue pigments.
Cosmic origin
Where Cobalt comes from
Supernovae
Formed in explosive burning near the iron peak and released by supernovae.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 27
- Atomic mass
- 58.933
- Category
- Transition metals
- Group · Period
- 9 · 4
- Block
- d-block
- Shells
- 2 · 8 · 15 · 2