Cobalt (Co)


  • Symbol: Co
  • Atomic Number: 27
  • Atomic Weight: 58.933194
  • Element Classification: Transition Metal
  • Discovered By: Georg Brandt
  • Discovery Date: 1735
  • Name Origin: German: ‘kobalt’ or ‘kobold’ meaning “goblin” or “evil spirit”
  • Density(g/cc): 8.86
  • Melting Point: 1495°C
  • Boiling Point: 2927°C
  • Appearance: Hard, lustrous, silver-gray metal
  • Atomic Radius(pm): 125


Cobalt was discovered by Swedish chemist Georg Brandt in 1735 when he was studying minerals that gave glass a deep blue color. Brandt was the first to demonstrate that the blue color was due to a new metal, not bismuth, as previously thought. The name cobalt comes from the German word ‘kobalt’ or ‘kobold’, which means goblin or evil spirit. The miners gave it this name because cobalt-containing ores were poisonous and, despite their efforts, yielded no copper.

Relation to Other Elements

Cobalt is a transition metal, located in group 9 of the periodic table, between iron and nickel. Like other transition metals, cobalt is hard, lustrous, and has a high melting point. It is ferromagnetic and can retain its magnetic properties up to 1100°C, the highest temperature of all the magnetic elements. Cobalt commonly exhibits the +2 and +3 oxidation states, forming various compounds that are useful in industry and technology.

Natural Occurrence

Cobalt is relatively rare in the Earth’s crust and is found in combination with nickel in meteoric iron. The primary cobalt ores are cobaltite (CoAsS), erythrite (Co₃(AsO₄)₂·8H₂O), glaucodot (Co,Fe)AsS, and skutterudite (Co,Ni)As₃. Cobalt is also a byproduct of nickel and copper mining. The Democratic Republic of Congo is a major source of cobalt ore.


Cobalt has several important applications:

  • Alloys: Cobalt is used in superalloys for aircraft engine parts, in steel-belted radial tires, and in alloys that retain their properties at high temperatures.
  • Batteries: Cobalt is a critical component in lithium-ion batteries, which power electronic devices, electric vehicles, and renewable energy systems.
  • Catalysts: Cobalt compounds are used as catalysts in the petroleum and chemical industries, including the Fischer-Tropsch process to convert natural gas into liquid fuels.
  • Pigments: Cobalt produces distinctive blue pigments, cobalt blue (cobalt aluminate, CoAl₂O₄), used in ceramics, glass, paints, and varnishes.
  • Radiotherapy: Cobalt-60, a radioactive isotope, is used in radiotherapy for cancer treatment, as well as in industrial radiography to inspect metal parts and welds.

The discovery of cobalt has significantly impacted various industries, particularly in materials science, energy storage, and medical treatment. Its unique properties, including magnetic characteristics and the ability to withstand high temperatures, make cobalt an invaluable resource in the development of advanced technologies and sustainable solutions.


Iron (Fe)

Nickel (Ni)