PTL:Tungsten
From ChemEd Collaborative
Tungsten is a transition metal in Group VIB (Group 6) and the 6th period. It has oxidation numbers ranging from 0 to +6, with +6 being common and +2, +3, +4, and +5 less so. Other members of Group VIB are chromium (Cr) and molybdenum (Mo). In the solid state, the metal has a body-centered cubic structure.
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Discovered
The elements of Group VIB were all discovered in a 20 year period at the end of the 18th century. In 1781 the Swedish chemist Scheele, along with Bergman, isolated an oxide of an unknown element from the mineral scheelite (CaWO4), then called "tungsten", from the Swedish tung sten for "heavy stone". Two years later Spanish brothers J.J. and F.d'Elhuyar isolated the same oxide from the mineral wolframite [(Fe, Mn)WO4], and they obtained the metal by reducing the oxide with charcoal.
WO3(s) + 3 C(s) 
W(s) + 3 CO(g)
Name
The name "wolfram", from which the symbol W is derived, is the internationally recommended name and is still used in the German literature. However, tungsten is used in the English-speaking world.
Characteristics
Tungsten's abundance in the earth's crust is about the same as that of molybdenum (about 1.2 ppm).
The pure metal is steel-gray and can be forged, spun, drawn into wire, or extruded. It has the highest melting point and lowest vapor pressure of all the known metals and so is an ideal material for [lamp filaments]. Its coefficient of thermal expansion is about the same as that of borosilicate glass, so it is excellent for making metal-to-glass seals. Although it will oxidize in air at high temperature, it is quite resistant to corrosion and is attacked only slightly by mineral acids.
Thermodynamic Characteristics
Studies of tungsten show that it has many abnormal thermodynamic properties. It has a high melting point, entropy of fusion, and expansion on melting. Of all the elements, it is only second to the graphite form of carbon for its melting point. These abnormal properties are believed to come from tungsten’s structural dependence on its d-electron states.
Because of its high melting point, the actual temperature of Tungsten is measured in many experiments using the brightness of the Tungsten calculated with a disappearing filament optical pyrometer. This gives the brightness temperature of Tungsten which is then converted into the actual temperature using the Wien’s equation.
Uses
Tungsten disulfide, WS2, is made by heating the metal with sulfur at 900°C. It forms an adhering, soft film on a variety of surfaces and is a good lubricant. (Note: MoS2 is also an excellent lubricant.)
Tungsten carbide, WC, is an interstitial compound. It is very stable to high temperatures and very hard. As a result it is used in [cutting tools]. About 67% of the tungsten produced is used in this manner.
Emission Spectra
This is the emission spectra for Tungsten.
