Tungsten and Wolfram are the names given to element 74 of Mendeleev's Periodic Table of the Chemical Elements. Its chemical symbol is W.
Tungsten has the highest melting point of all metals (3,422± 15°C). At this temperature most of the other engineering metals (Fe, Al, Cu, Ti) have already vaporised. Its boiling point of about 5,700°C corresponds to the surface of the sun. With its density of 19.25g/cm3, tungsten is also among the heaviest metals. Its electrical conductivity at 0°C is about 28% of that of silver, which itself has the highest conductivity, and its coefficient of thermal expansion is the lowest of all metals.
Tungsten features the lowest vapour pressure of all metals, very high moduli of compression and elasticity, very high thermal creep resistance and high thermal and electrical conductivity. Tungsten is the most important metal for thermo-emission applications, not only because of its high electron emissivity (which is caused by additions of foreign elements) but also because of its high thermal and chemical stability.
Tungsten is a shiny white metal and, in its purest form, is quite pliant and can easily be processed. Usually, however, it contains small concentrations of carbon and oxygen, which give tungsten metal its considerable hardness and brittleness. For decades, scientists have worked to overcome the brittleness problem.
Most of these unusual properties are due to the half-filled 5d electron shells (d5s1) with a very high binding energy of the tungsten in the bcc tungsten crystal arising from the strong, unsaturated covalent bonds. Based on these properties, tungsten, tungsten alloys and some tungsten compounds cannot be substituted in many important applications in different fields of modern technology.