About

Cobalt is a hard, lustrous, silvery-blue metal that is ferromagnetic. It is used to create strong, corrosion-resistant, and high-temperature alloys, as well as powerful magnets. Its compounds have been used for centuries to create a deep blue color in glass, ceramics, and paints (cobalt blue). It is also a critical component in the cathodes of many lithium-ion batteries.

Atomic Properties

Atomic Number27

Atomic Weight58.933 u

Neutrons (common)32

Electron Configuration[Ar] 3d⁷ 4s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²

Electrons per Shell2, 8, 15, 2

Electronegativity1.88

Electron Affinity63.896 kJ/mol

Oxidation States+2, +3

Covalent Radius126 pm

Van der Waals Radius192 pm

Ionic Radius74.5 pm

Periodic Table Position

Group9

Period4

BlockD

Chemical SeriesTransition metals

Physical Properties

State at STPsolid

Appearancehard, lustrous, silver-gray metal

Crystal Structurehcp

Magnetic Orderingferromagnetic

Speed of Sound4,720 m/s

Poisson Ratio0.31

Thermal Properties

Melting Point1,768 K

Boiling Point3,200 K

Thermal Expansion13 1/K

Thermal Conductivity100 W/(m·K)

Specific Heat0.421 J/(g·K)

Molar Heat24.81 J/(mol·K)

Heat of Fusion16.06 kJ/mol

Heat of Vaporization377 kJ/mol

Abundance

In Earth's Crust25 ppm

In Ocean0 ppm

In Solar System25 ppm

In Human Body0.02 ppm

In Universe3 ppm

Discovery

Discovered byGeorg Brandt

Discovery Year1,735

Occurrenceprimordial

CAS Number7440-48-4

Electron Configuration

Energy

↿⇂

↿

Isotopes of Cobalt

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
⁵⁵Co	54.941995	—	17.53 h	Positron Emission, Electron Capture
⁵⁶Co	55.939839	—	77.236 d	Electron Capture, Positron Emission
⁵⁷Co	56.936291	—	271.811 d	Electron Capture
⁵⁸Co	57.935752	—	70.844 d	Electron Capture, Positron Emission
⁵⁹Co	58.933190	100%	Stable	Stable
⁶⁰Co	59.933820	—	5.2714 y	Beta Minus Decay

Interactive Visualization

Explore the 3D Bohr model of Cobalt in our interactive viewer.

View 3D Model of Cobalt