Metallic chemical element, one of the transition elements, chemical symbol W, atomic number 74. Exceptionally strong, white to grayish, and brittle, it has the highest melting point (6,170 °F [3,410 °C]), greatest high-temperature strength, and lowest thermal expansion coefficient of any metal. Its chief uses are in steels to increase hardness and strength and in lightbulb filaments (see incandescent lamp). It is also used in electrical contacts, rocket nozzles, chemical apparatus, high-speed rotors, and solar-energy devices. Tungsten is relatively inert, but compounds (in which it has various valences) are known. The most important, tungsten carbide, noted for its hardness, is used to increase the wear-resistance of cast iron and of tools' cutting edges.
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A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite. It is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Tungsten is often brittle and hard to work in its raw state; however, if pure, it can be cut with a hacksaw. The pure form is used mainly in electrical applications, but its many compounds and alloys are used in many applications, most notably in light bulb filaments, X-ray tubes (as both the filament and target), and superalloys. Tungsten is also the only metal from the third transition series that is known to occur in biomolecules.
Another 30 artificial radioisotopes of tungsten have been characterized, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days, 178W with a half-life of 21.6 days, and 187W with a half-life of 23.72 h. All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives that are less than 8 minutes. Tungsten also has 4 meta states, the most stable being 179mW (T½ 6.4 minutes).