Cobalt (Co)

Stable Isotopes of Cobalt 

Isotope Z(p) N(n) Atomic Mass Natural Abundance Nuclear Spin
Co-59  27 32  58.93320 100.00%  7/2- 


Cobalt was discovered in 1735 by Georg Brandt. Its name derives from the German word kobald, meaning "goblin" or "evil spirit." Minerals containing cobalt were used by the early civilizations of Egypt and Mesopotamia for coloring glass deep blue. Cobalt oxide is used today to add a pink or blue color to glass. It is also an important trace element in soils and necessary for animal nutrition. The most important modern use of cobalt is in the manufacture of various wear-resistant and superalloys. Its alloys have shown high resistance to corrosion and oxidation at high temperatures. Radioactive Cobalt-60 is used in radiography and in the sterilization of food.

A silvery-white, shining, hard, ductile, somewhat malleable metal, cobalt is also ferromagnetic, with permeability two-thirds that of iron. It has exceptional magnetic properties in alloys. It is attached by dilute hydrochloric and sulfuric acids. It corrodes readily in air, and it has unusual coordinating properties, especially the trivalent ion. It is noncombustible except in powder form.

Cobalt occurs in two allotropic modifications over a wide range of temperatures: the crystalline close-packed-hexagonal form is known as the alpha form, which turns into the beta (or gamma) form above 417 ºC.

In finely powdered form, cobalt ignites spontaneously in air. Reactions with acetylene and bromine pentafluoride proceed to incandescence and can become violent. The metal is moderately toxic by ingestion. Inhalation of dusts can damage lungs. Skin contact with powdered material can cause dermatitis.

Properties of Cobalt

Name Cobalt 
Symbol Co 
Atomic number 27 
Atomic weight 58.933 
Standard state Solid at 298 °K 
CAS Registry ID 7440-48-4 
Group in periodic table
Group name None 
Period in periodic table
Block in periodic table d-block 
Color Lustrous, metallic, grayish tinge 
Classification Metallic 
Melting point 1495 °C
Boiling point 2870 °C
Thermal conductivity 100 W/(m·K) at 298.2 °K
Electrical resistivity 5.6 µΩ·cm at 20 °C 
Electronegativity 1.8 
Specific heat 421 J/kg K
Heat of vaporization 375 kJ·mol-1
Heat of fusion 16.2 kJ·mol-1
Density of solid 8.86 g/cm3
Electron configuration [Ar]3d74s2
Oxidation states  0, +1, +2, +3, +4, +5 

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