Tungsten, also called wolfram, is a fairly hard, silver-white metallic element. Tungsten remains strong at high temperatures. It melts at about 3422 °C, the highest melting temperature of any metal. Manufacturers often use tungsten to make equipment that must withstand extreme heat. Tungsten’s chemical symbol is W.
Manufacturers add tungsten to steel to make the steel stronger and more elastic. Tungsten steel tools last longer than ordinary steel tools. Tungsten and carbon form tungsten carbide (WC), an extremely hard substance used in the tips of mining drills and high-speed cutting tools. Electronics manufacturers use heating filaments made of tungsten in vacuum tubes for television sets and other electronic equipment. Filaments for electric lights and contact points for the ignition systems of automobiles are also made of tungsten.
Tungsten can combine with either calcium or magnesium to form chemical compounds called phosphors. Phosphors give off visible light when exposed to certain kinds of energy. Tungsten-containing phosphors convert ultraviolet rays into visible light in some fluorescent lamps.
Tungsten trioxide (WO3) can mix with elements called alkali metals to form a class of compounds known as tungsten bronzes. Tungsten bronzes that have nearly equal amounts of alkali ions and tungsten ions are good electrical conductors, while those with fewer alkali ions are semiconductors. Tungsten bronzes are colorful and have been used as pigments in paint.
Tungsten occurs in nature in the minerals scheelite (CaWO4) and wolframite ([Fe,Mn]WO4). The element’s name comes from scheelite, which the Swedish once called tung sten, meaning heavy stone. Scheelite was later renamed in honor of the Swedish chemist Carl Wilhelm Scheele. In 1781, Scheele became the first person to isolate an oxide of tungsten. He extracted tungsten trioxide from scheelite. In 1783, two brothers, the Spanish chemists Fausto and Juan Jose de Elhuyar, used wolframite to prepare the first sample of tungsten metal.
Workers use a variety of chemical processes to extract tungsten metal from wolframite and scheelite. Most of these methods produce crystals of a compound called ammonium paratungstate. These crystals are then heated to produce tungsten trioxide. Workers usually heat tungsten trioxide with hydrogen at around 850 °C to produce pure tungsten. China produces most of the world’s tungsten.
Tungsten’s atomic number (number of protons in its nucleus) is 74. Its relative atomic mass is 183.84. An element’s relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of carbon 12, the most stable isotope of carbon. Tungsten boils at about 5555 °C.
Chemists classify tungsten as a transition metal . For information on the position of tungsten on the periodic table, see the article Periodic table .
See also Alloy (Alloys of iron) ; Electric light (Incandescent lamps) ; Element, Chemical (tables) ; Wolframite .
