Tungsten (atomic number 74, element symbol W) is a steel-gray to silver-white metal, familiar to many people as the metal used in incandescent light bulb filaments. Its element symbol W derives from an old name for the element, wolfram. Here are 10 interesting facts about tungsten:
- Tungsten is element number 74 with atomic number 74 and atomic weight 183.84. It is one of the transition metals and has a valence of 2, 3, 4, 5, or 6. In compounds, the most common oxidation state is VI. Two crystal forms are common. The body-centered cubic structure is more stable, but another metastable cubic structure may coexist with this form.
- The existence of tungsten was suspected in 1781, when Carl Wilhelm Scheele and T.O. Bergman made previously unknown tungstic acid from a material now called scheelite. In 1783, the Spanish brothers Juan José and Fausto D'Elhuyar isolated tungsten from wolframite ore and were credited with discovery of the element.
- The element name wolfram came from the name of the ore, wolframite, which derives from the German wolf's rahm, which means "wolf's foam". It got this name because European tin smelters noticed the presence of wolframite in tin ore reduced the tin yield, appearing to eat tin like a wolf would devour sheep. What many people do not know is that the Delhuyar brothers actually proposed the name volfram for the element, as w was not used in the Spanish language at that point. The element was known as wolfram in most European countries, but called tungsten (from Swedish tung sten meaning "heavy stone", referencing the heaviness of scheelite ore) in English. In 2005, the International Union of Pure and Applied Chemistry dropped the name wolfram entirely, to make the periodic table the same in all countries. This is probably one of the most highly disputed name changes made on the periodic table.
- Tungsten has the highest melting point of the metals (6191.6 °F or 3422 °C), lowest vapor pressure, and the highest tensile strength. Its density is comparable to that of gold and uranium and 1.7 times higher than that of lead. While the pure element may be drawn, extruded, cut, forged, and spun, any impurities make tungsten brittle and difficult to work.
- The element is conductive and resists corrosion, although metal specimens will develop a characteristic yellowish cast upon exposure to air. A rainbow oxide layer is also possible. It is the 4th hardest element, after carbon, boron, and chromium. Tungsten is susceptible to slight attack by acids, but resists alkali and oxygen.
- Tungsten is one of the five refractory metals. The other metals are niobium, molybdenum, tantalum, and rhenium. These elements are clustered near each other on the periodic table. Refractory metals are those which exhibit extremely high resistance to heat and wear.
- Tungsten is considered to have low toxicity and plays a biological role in organisms. This makes it the heaviest element used in biochemical reactions. Certain bacteria use tungsten in an enzyme that reduces carboxylic acids to aldehydes. In animals, tungsten interferes with copper and molybdenum metabolism, so it is considered slightly toxic.
- Natural tungsten consists of five stable isotopes. These isotopes actually do undergo radioactive decay, but the half-lives are so long (four quintillion years) that they are stable for all practical purposes. At least 30 artificial unstable isotopes have also been recognized.
- Tungsten has many uses. It is used for filaments in electric lamps, in television and electron tubes, in metal evaporators, for electrical contacts, as an x-ray target, for heating elements, and in numerous high temperature applications. Tungsten is a common element in alloys, including tool steels. Its hardness and high density also make it an excellent metal for constructing penetrating projectiles. Tungsten metal is used for glass-to-metal seals. The element's compounds are used for fluorescent lighting, tanning, lubricants, and paints. Tungsten compounds find use as catalysts.
- Sources of tungsten include the minerals wolframite, scheelite, ferberite, and huebnertie. It's believed about 75% of the world's supply of the element is found in China, although other ore deposits are known in the US, South Korea, Russia, Bolivia, and Portugal. The element is obtained by reducing tungsten oxide from the ore with either hydrogen or carbon. Producing the pure element is difficult, due to its high melting point.