An Overview about the Chemical Element Cobalt


Symbol: Co

Atomic Number: 27

Atomic Mass: 58.9332 amu (atomic mass units)

Melting Point: 1495.0 C (1768.15 K, 2723.0 F)

Boiling Point: 2870.0 C (3143.15 K, 5198.0 F)

Number of Protons: 27

Number of Electrons: 27

Number of Neutrons: 32

Classification: Transition Metal

Crystal Structure: Hexagonal

Density @ 293 K: 8.9 grams per cubic centimeter

Color: silver

The transition metal cobalt was discovered in 1773 by the Swedish chemist George Brandt. He was investigating the cause of a blue coloration of glass at the time it was erroneously thought this color was due to the element bismuth. Its name comes from the German word for evil spirit “kobald” or “kobalt” also from the Greek word for mine “cobalos”.

Cobalt is one of only three elements which can produce a magnetic field. The other two elements are iron and nickel.

There is one naturally occurring isotope of cobalt that is cobalt-59 which is stable. A number of unstable isotopes of the element have been made. They have mass numbers ranging from 48 to 75. One of these unstable isotopes, cobalt-60, has important uses in medicine. It is used to treat some forms of cancer as well as being used as a medical tracer. Cobalt-60 produces gamma rays and decays by beta decay to form nickel-60. Cobalt-60 also has the longest half-life of the unstable isotopes at 5.27 years. Cobalt-49 has the shortest half-life at less than 35 nanoseconds and decays by either electron capture or proton emission.

The element as an important role in nutrition as it is found in vitamin B12.

While cobalt can be recovered from the mineral ores cobaltite or erythrite it is more commonly obtained as a by-product from the mining and processing of other metals. Mines producing: nickle ,silver, lead, copper and iron all are sources of cobalt. There are a number of industrial uses for the element.

* Alnico is an alloy of aluminum, nickel and cobalt that is used to make permanent magnets.

* Another alloy of cobalt which also contains tungsten and chromium is known as stellite. This alloy is used to produce high speed, high temperature cutting tools.

* Cobalt alloys are also used in the manufacture of jet engines and gas turbines.

* Some stainless steels contain are an alloy of cobalt as are some magnetic steels.

* Cobalt can be electroplated on to other metals to give a decorative finish which will resist tarnishing by oxidation.

* Compounds of cobalt such as cobalt blue, cobalt green, cobalt yellow and new blue are used to give color to glass, ceramics and enamels.

* When combined with the rare earth element samarium cobalt can form permanent magnets with the highest known resistance to demagnetization. These magnets are being employed as magnetic pickups in electric guitars and other similar musical instruments.