Science / Periodic Table of Elements / Cobalt (Co): Atomic number: 27, Atomic mass: 58.9332 g.mol -1, Electronegativity: 1.8, Density: 8.9 g.cm-3 at 20Â°C, Melting point: 1495 Â°C, Boiling point: 2927 Â°C, Vanderwaals radius: 0.125 nm, Ionic radius: 0.078 nm (+2) ; 0.063 nm (+3), Isotopes: 8, Electronic shell: [ Ar ] 3d7 4s2, Energy of first ionisation: 757 kJ.mol -1, Energy of second ionisation: 1666.3 kJ.mol -1, Energy of third ionisation: 3226 kJ.mol -1, Standard potential: - 0.28 V ( Co2+/ Co ) ; +1.84 V ( Co3+/ Co2+ ), Discovered by: George Brandt in 1737. Cobalt is a hard ferromagnetic, silver-white, hard, lustrous, brittle element. It is a member of group VIII of the periodic table. Like iron, it can be magnetized. It is similar to iron and nickel in its physical properties. The element is active chemically, forming many compounds. Cobalt is stable in air and unaffected by water, but is slowly attacked by dilute acids. Applications: Cobalt is used in many alloys (superalloys for parts in gas turbine aircrafr engines, corrosion resistant alloys, high-speed steels, cemented carbides), in magents and magnetic recording media, as catalysts for the petroleum and chemical industries, as drying agents for paints and inks. Cobalt blue is an important part of artists' palette and is used bu craft workers in porcelain, pottery, stained glass, tiles and enamel jewellery. The radioactive isotopes, cobalt-60, is used in medical treatment and also to irradiate food, in order to preserve the food and protect the consumer. Cobalt in the enviroment: Most of the Earth's cobalt is in its core. Cobalt is of relatively low abundance in the Earth's crust and in natural waters, from which it is precipitated as the highly insoluble cobalt sulfine CoS. Although the average level of cobalt in soils is 8 ppm, there are soils with as little as 0.1 ppm and others with as much as 70 ppm. In the marine environment cobalt is needed by blue-green algae (cyanobacteria) and other nitrogen fixing organisms. Cobalt is not found as a free metal and is generally found in the form of ores. Cobalt is usually not mined alone, and tends to be produced as a by-product of nickel and copper mining activities. The main ores of cobalt are cobaltite, erythrite, glaucodot, and skutterudite. The world's major producers of cobalt are the Democratic Republic of the Congo, mainland China, Zambia, Russia and Australia. It is also found in Finland, Azerbaijan, and Kazakhstan. World production is 17.000 tonnes per year.
Science / Periodic Table of Elements / Cobalt (Co): Atomic number: 27, Atomic mass: 58.9332 g.mol -1, Electronegativity: 1.8, Density: 8.9 g.cm-3 at 20Â°C, Melting point: 1495 Â°C, Boiling point: 2927 Â°C, Vanderwaals radius: 0.125 nm, Ionic radius: 0. MORE
Health / Dentistry / Chrome Cobalt Molybdenum: A surgical metal alloy used to fabricate cast custom implants. MORE