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Tungsten (W)

Science / Periodic Table of Elements / Tungsten (W): Atomic number: 74, Atomic mass: 183.85 g.mol -1, Electronegativity accoridin to Pauling: 1.7, Density: 19.3 g.cm-3 at 20?°C, Melting point: 3410 ?°C, Boiling point: 5660 ?°C, Vanderwaals radius: 0.137 nm, Ionic radius: 0.068 nm (+4) ; 0.067 nm (+6), Isotopes: 10, Electronic shell: [ Xe ] 4f14 5d4 6s2, Energy of first ionisation: 768.6 kJ.mol -1, Standard potential: - 0.05 V ( W+4/ W ), Discovered by: Fausto and Juan Jose de Elhuyar in 1783. Tungsten is a lustrous and silvery white metal. The bulk metal resists attack by oxygen, acids and alkalis. Tungsten has the highest melting point of any metal. Applications: Tungsten is used in filaments in incandescent light bulbs, it is also used in electric contacts and arc-welding electrodes. Tungsten is used in alloys, such as steel, to which it imparts great strength. Cement carbide is the most important use for tungsten: its main component is tungsten carbide (WC). It has the strength to our cast iron and it makes excellent cutting tools for the machining of steel. X-ray tubes for medical use have a tungsten emitter coil and the screen used to view X-rays rely on calcium and magnesiumtungstate phosphors to convert X-rays into blue visible light. Tungsten is also used in microchip tecnology and liquid crystals displays. Tungsten in the environment: Very little tungsten has been detetced in the dew soils that have been analysed for it, although around an ore-processin plant in Russia levels as high as 2000 ppm were found. The concentration of the element in natural waters is very low. There are several minerals of tungsten, the most important are scheelite and wolframite. The main mining area is China, which today accounts for more than two-thirds of the world's supply. Other places with active tungsten mines are Russia, Austria, Bolivia, Peru and Portugal. World production is around 40.000 tonnes per year and reserves are estimated to be around 5 million tonnes. Tungsten is also recycled and it meets 30% of demand.
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