Tungsten

Tungsten was discovered in 1783, it is also known as wolfram as it is an exceptionally strong metal. It has the highest melting and boiling points and alloys of tungsten are used in various high-temperature applications.

History and Discovery

Tungsten has been known since prehistoric times, around 350 years ago when Chinese porcelain used peach colored tungsten pigment. It was isolated as a novel element by Juan Jose and Fausto Elhuyar in 1783, through charcoal reduction of the oxide which was derived from wolframite (ore of tungsten). However, few year earlier, Carl Wilhelm Scheele (1781) investigated and isolated the white oxide and referred it as the new acid, tungstic acid also called scheelite. Th e names tungsten and wolfram have been used since its discovery. In British and America Tungsten is more common, while in Germany and other European countries Wolfram is preferred [1]. The word Tungsten has been derived from Swedish language that means “heavy stone” and wolframite is derived from German “wolf rahm” that means “wolf cream”.

Tungsten

Periodic Table ClassificationGroup 4
Period 6
State at 20CSolid
ColorGrayish white, lustrous
Electron Configuration[Xe] 4f14 5d4 6s2
Electron Number74
Proton Number74
Electron Shell2, 8, 18, 32, 12, 2
Density19.35 g.cm-3 at 20°C
Atomic number74
Atomic Mass183.84 g.mol -1
Electronegativity according to Pauling2.36

Occurrence

Tungsten is an abundant element and is present in about 1.5 parts per million in the earth’s crust. Tungsten do not occur as a free metal. It is as abundant as tin and molybdenum and occur in the form of minerals like scheelite (calcium tungstate), wolframite (tin ore in around granite), huebnertie (manganese) and ferberite (iron). The main producers of tungsten in the world are China, Russia and Portugal.

Physical Characteristics

Tungsten is a transition metal.  Raw tungsten steel-grey metal that is hard and brittle. It has very high melting point about, 3422oC and boiling point is about 5930oC. It has ability to retain its strength at very high temperatures. Its density is also very high, about 19.3 times that of water. There are two allotropic forms of tungsten: polycrystalline tungsten is hard, and which makes it difficult to work with but pure single crystalline tungsten is soft and can be cut with hard steel hacksaw. Tungsten atomic number is 74 and atomic mass number is 183.85 [2].

Chemical Characteristics

Tungsten is not very reactive metal. It does not react with oxygen at room temperature. It also resists attacks by acids and alkalis. The most common oxidation state of tungsten is +6 but it exists in all oxidation states from -2 to +6. In powdered form, tungsten reacts with carbon to produce tungsten carbide upon heating. It is mostly resistant to chemical attack but reacts with chlorine to form tungsten hexachloride [3]. Higher oxidation states compounds of tungsten form oxides and they are relevant to their terrestrial occurrence while mid -level oxidation states compounds form metal clusters and low oxidation states are associated with the formation of CO complexes.

Significance and Uses

  • Tungsten is used to make material with high tensile strength, such as tungsten carbide that has a melting point of 2770o
  • Tungsten is used to make wear resistant abrasives cutting tools, such as knives.
  • Tungsten is used to make heavy metal alloys.
  • Tungsten alloys are widely used in aerospace and automotive industries.
  • Tungsten with steel is used in making hard permanent magnets.
  • Tungsten is widely used in mining, construction, electrical and metal working machinery.
  • Tungsten is used as the filament in incandescent light bulbs.
  • Tungsten (IV) sulfide is a high temperature lubricant and component of catalyst for hydrodesulfurization (remove sulfur from natural gas).
  • Oxides of tungsten are used in manufacturing of ceramic glazes.
  • Tungsten salts are widely used in chemical and tanning industries.
  • Tungsten is also used in printing nozzle for 3D printing.
  • Tungsten is similar with gold in respect of density and is used in jewelry as an alternative of gold.
  • Elemental tungsten due to its high melting point make it useful for cathode ray tube and vacuum tube.

Health Hazards

In biological systems, the action of tungsten is antagonistic to molybdenum, which leads to the inhibition of action of various oxidative enzymes, for instance xanthine oxidase. The effect of tungsten on environment is quite limited. In the workplace, people can be exposed to tungsten via inhalation, skin contact and eye contact but has no harmful health effects.

Isotopes of Tungsten

Tungsten has five stable isotopes: Tungsten-180, tungsten-182, tungsten-183, tungsten-184 and tungsten-186. Thirty artificial radioactive isotopes also have been characterized, in which the most stable is 181W, with the half-life of 121.2 days [4].

REFERENCES

[1]. https://www.britannica.com/science/tungsten-chemical-element

[2]. https://www.thebalance.com/metal-profile-tungsten-2340159

[3]. Daintith, John (2005). Facts on File Dictionary of Chemistry(4th ed.). New York: Checkmark Books. ISBN 0-8160-5649-8.

[4]. Sonzogni, Alejandro. “Interactive Chart of Nuclides”. National Nuclear Data Center: Brookhaven National Laboratory. Archived from the original on 2008-05-22.