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It's Elemental

The Element Cobalt

[Click for Isotope Data]


27 Co Cobalt 58.933194

Atomic Number: 27

Atomic Weight: 58.933194

Melting Point: 1768 K (1495°C or 2723°F)

Boiling Point: 3200 K (2927°C or 5301°F)

Density: 8.86 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 4

Group Number: 9

Group Name: none

What's in a name? From the German word for goblin or evil spirit, kobald and the Greek word for mine, cobalos.

Say what? Cobalt is pronounced as KO-bolt.

History and Uses:

Cobalt was discovered by Georg Brandt, a Swedish chemist, in 1739. Brandt was attempting to prove that the ability of certain minerals to color glass blue was due to an unknown element and not to bismuth, as was commonly believed at the time. Cobalt's primary ores are cobaltite (CoAsS) and erythrite (Co3(AsO4)2). Cobalt is usually recovered as a byproduct of mining and refining nickel, silver, lead, copper and iron.

Although cobalt is used in electroplating to give objects an attractive surface that resists oxidation, it is more widely used to form alloys. Alnico, an alloy consisting of aluminum, nickel and cobalt is used to make powerful permanent magnets. Stellite alloys, which contain cobalt, chromium and tungsten, are used to make high-speed and high temperature cutting tools and dyes. Cobalt is also used to make alloys for jet engines and gas turbines, magnetic steels and some types of stainless steels.

Cobalt-60, a radioactive isotope of cobalt, is an important source of gamma rays and is used to treat some forms of cancer and as a medical tracer. Cobalt-60 has a half-life of 5.27 years and decays into nickel-60 through beta decay.

Cobalt compounds have been used for centuries to color porcelain, glass, pottery, tile and enamel. Some of these compounds are known as: cobalt blue, ceruleum, new blue, smalt, cobalt yellow and cobalt green. In addition to being used as a dye, cobalt is also important to human nutrition as it is an essential part of vitamin B12.

Estimated Crustal Abundance: 2.5×101 milligrams per kilogram

Estimated Oceanic Abundance: 2×10-5 milligrams per liter

Number of Stable Isotopes: 1 (View all isotope data)

Ionization Energy: 7.881 eV

Oxidation States: +3, +2

Electron Shell Configuration:


2s2   2p6

3s2   3p6   3d7


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For questions about this page, please contact Carol McKisson.