Tungsten

74

W

183.84(1)

  • Name: Tungsten
  • Symbol: W
  • Atomic number: 74
  • Atomic weight: 183.84(1)
  • CAS Registry ID: 7440-25-7
  • Group name: (none)
  • Period number: 6
  • Block: d-block
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Description

Tungsten is a transition metal that has a shiny grey white color in its natural solid state. It is soft enough to be cut with a hacksaw in its pure form, but it is a brittle metal. Tungsten has an atomic weight of 183.84, a melting point of 6192 °F, and a boiling point of 10031 °F. Some common uses of tungsten include: as a component in cemented carbides, as a filament in light bulbs, alloyed with other metals to create heavy metal alloys, and as a component in turbine blades.

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Isolation

Tungsten occurs most often in nature with minerals such as wolframite and scheelite. The isolation procedure is lengthy as tungsten does not occur in its free state in nature.

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There are a few different ways that tungsten can be concentrated and isolated. The first step takes mixed ore residues and low grade tungsten ore and subjects the ore to roasting and leaching using soda. This solution is purified using the calcium oxide of wolframite which results in the decomposition of tungsten to tungstic acid. The acid is dissolved in an ammonia solution and crystallization of the tungsten results in ammonium paratungstate. Hydrogen and carbon applications further isolate the tungsten.

Isolation of high grade tungsten ore also begins with treating the ore with soda or a caustic autoclave leach. Further purification is performed along with a liquid or solid ion exchange. The products that result from crystallization are ammonium paratungstate which are further reduced using hydrogen and carbon applications. Tungsten can also be recycled and isolated again from tungsten scrap metals; in this process the scrap is oxidized and chemically processed again to ammonium paratungstate.


General
Name Tungsten
Symbol W
Number 74
Chemical series transition metals
Group 6
Period 6
Block d
Appearance grayish white, lustrous
Standard atomic weight 183.84(1)  g·mol−1
Electron configuration [Xe] 4f14 5d4 6s2
Electrons per shell 2, 8, 18, 32, 12, 2
Atomic properties
Crystal structure cubic body centered
Oxidation states 6, 5, 4, 3, 2, 1, 0, −1 (mildly acidic oxide)
Electronegativity 2.36 (scale Pauling)
Ionization energies 1st: 770 kJ/mol
(more) 2nd: 1700 kJ/mol
(more)
Atomic radius 135 pm
Atomic radius (calc.) 193 pm
Covalent radius 146 pm
Van der Waals radius
Physical properties
Phase solid
Density (near r.t.) 19.25  g·cm−3
Liquid density at m.p. 17.6  g·cm−3
Melting point 3695 K (3422 °C, 6192 °F)
Boiling point 5828 K (5555 °C, 10031 °F)
Critical point
Heat of fusion 52.31  kJ·mol−1
Heat of vaporization 806.7  kJ·mol−1
Heat capacity (25 °C) 24.27  J·mol−1·K−1
Miscellaneous
Magnetic ordering
Electrical resistivity (20 °C) 52.8 n Ω·m
Thermal conductivity (300 K) 173  W·m−1·K−1
Thermal expansion (25 °C) 4.5  µm·m−1·K−1
Speed of sound (thin rod) (r.t.) (annealed) 4620  m·s−1
Young's modulus 411 GPa
Shear modulus 161 GPa
Bulk modulus 310 GPa
Poisson ratio 0.28
Mohs hardness 7.5
Vickers hardness 3430 MPa
Brinell hardness 2570 MPa
CAS registry number 7440-33-7

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