Tungsten is a metal element, the element symbol is W. It has high hardness, high melting point, and is not corroded by air at room temperature; it is mainly used to manufacture filaments, high-speed cutting alloy steel, super-hard molds, and also used in optical instruments and chemical instruments. China is the world's largest tungsten storage country.
The atomic number of tungsten is 74, the relative atomic mass is 183.85, the atomic radius is 137 picometers, and the density is 19.35 grams per cubic centimeter. It belongs to the VIB group of the sixth period (the second longest period) of the periodic table. Tungsten is mainly a hexavalent cation in nature, and its ionic radius is 0.68×10-10m. Due to the small ion radius of w6+, high electricity price, strong polarization ability, and easy to form complex anions, tungsten is mainly in the form of complex anions [Wo4]2-, which combines with Fe2+, Mn2+, ca2 and other cations in the solution to form wolframite or Scheelite precipitation.