Cobalt

Symbol

Co

Atomic number

27

Atomic mass	58.9332		Thermal conductivity	1.00
Atomic radius	1.67		Covalent radius	1.16
Density	8.90		Atomic volume	6.7
Melting point	1768		Oxidation states	2,3
Boiling point	3143		Stable isotopes	1
Heat of vapor.	376.50		Electronegativity	1.88
Heat of fusion	16.190		First ionization	7.86
Specific heat	0.42		Electrical conduct.	...

Electron configuration

Cobalt

Cobalt is a silvery-white metal, with a slight reddish tinge. It occurs in the minerals smaltite and safflorite with the composition CoAs₂. Cobalt also forms an arsenide with the content CoAs_2-3 which is called skutterudite. The sulfide mineral cobaltite, CoAsS, also occurs. Cobalt is usually found in association with nickel. Cobalt forms the sulfide mineral linnaeite, Co₃S₄. Copper, cobalt and nickel join in the sulfide carrollite, Cu(Co,Ni)₂S₄. Cobalt joins with iron and arsenic in the sulfide glaucodot, (Co,Fe)AsS. Cobalt and nickel form the sulfide siegenite, CoNi₂S₄. Roselite is an arsenate that contains cobalt, magnesium and calcium and forms red crystals. Erythrite is an arsenate of cobalt and also shows a red or rose color.

Cobalt is used to produce the strongly ferromagnetic alloy alnico which is used to make strong permanent magnets. Alnico alloys iron, nickel, cobalt and aluminum.

Cobalt chloride (CoCl₂.6H₂O) forms red crystals which turn blue when dehydrated. Cobalt oxide, CoO, is a black powder, but it gives a blue color to glass when dissolved in it (cobalt glass).

Cobalt Nuclear Data

The decay of cobalt-57 by electron capture produces an excited state of iron-57 which emits gamma rays to reach its ground state. One of those transitions has become very important for Mossbauer effect studies.

The isotope Cobalt-60 has historical significance because it was a component in the radioactive fallout from nuclear weapons. The isotope was used for many years in radiation therapy for cancer. It was also the isotope associated with experiment which demonstrated the nonconservation of parity.