Tungsten (chemical element)

Tungsten is a kind of metal element, the symbol of which is w. it has high hardness, high melting point and is not corroded by air at normal temperature. It is mainly used for manufacturing filament, high-speed cutting alloy steel, superhard mould, optical instrument and chemical instrument. China is the largest tungsten storage country in the world.

Tungsten has a atomic number of 74, a relative atomic mass of 183.85, an atomic radius of 137 PICM and a density of 19.35 g / cm3. It belongs to the VIB group of the sixth period (the second long period) in the periodic table of elements. Tungsten is mainly hexavalent cation in nature, and its ionic radius is 0.68 × 10-10 M. Because W6 + ion radius is small, the electricity price is high, the polarization ability is strong, it is easy to form complex anion. Therefore, tungsten is mainly in the form of complex anion [WO4] 2 -, which combines with Fe2 +, Mn2 +, Ca2 + and other cations in the solution to form wolframite or scheelite precipitation. After smelting, tungsten is a silvery white lustrous metal with high melting point, high hardness, low vapor pressure, low evaporation rate and relatively stable chemical properties.