Tungsten

Characteristics and Physical Properties

• Tungsten is a hard steel-grey metal that is often brittle and hard to work.
• Purified, monocrystalline tungsten retains its hardness and becomes malleable.
• Tungsten has the highest melting point, lowest vapor pressure, and highest tensile strength among all metals.
• Tungsten has the lowest coefficient of thermal expansion of any pure metal.
• Alloying tungsten with steel increases its toughness.
• Tungsten has a melting point of 3,422°C and a boiling point of 5,930°C.
• Its density is 19.30 grams per cubic centimeter.
• Tungsten is intrinsically brittle but can be cut with a hard-steel hacksaw when in a pure single-crystalline form.
• Tungsten has a body-centered cubic structure (α phase) and a metastable A15 cubic structure (β phase).
• Tungsten has the lowest electrical resistivity in its α phase.

Isotopes

• Naturally occurring tungsten consists of four stable isotopes (182W, 183W, 184W, and 186W) and one long-lived radioisotope (180W).
• Only 180W has been observed to decay into isotopes of element 72.
• Tungsten has 34 artificial radioisotopes, with the most stable being 181W, 185W, 188W, 178W, and 187W.
• The half-life of 181W is 121.2 days, 185W is 75.1 days, and 188W is 69.4 days.
• Tungsten also has 11 meta states, with the most stable being 179mW (6.4 minutes).

Chemical Properties

• Tungsten is mostly non-reactive and does not react with water, most acids and bases, or oxygen at room temperature.
• It reacts with fluorine to form tungsten(VI) fluoride and with chlorine or bromine at elevated temperatures.
• Finely divided tungsten is pyrophoric.
• Tungsten typically exhibits oxidation states from -2 to +6, with +6 being the most common.
• Tungsten combines with oxygen to form tungstic oxide, which dissolves in aqueous alkaline solutions to form tungstate ions.

Applications

• Tungsten is used in incandescent light bulb filaments, X-ray tubes, and gas tungsten arc welding electrodes.
• It is used in superalloys and for radiation shielding due to its hardness and high density.
• Tungsten compounds are often used as industrial catalysts.
• Tungsten is suitable for military applications in penetrating projectiles.
• Tungsten is found in biomolecules in a few species of bacteria and archaea, but it is toxic to most forms of animal life.

Tungsten Compounds and Forms

• Tungsten compounds include paratungstate B anion, metatungstate anion, and heteropoly acids.
• Paratungstate B anion is less soluble, while metatungstate anion is very soluble.
• Metatungstate anion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the Keggin anion.
• Inclusion of different atoms, like phosphorus, in metatungstate produces heteropoly acids.
• Tungsten trioxide can form intercalation compounds with alkali metals, such as sodium tungsten bronze.
• Tungsten forms diatomic species W in gaseous form.
• Diatomic tungsten molecules feature a sextuple bond between tungsten atoms.
• This sextuple bond is the highest known bond order among molecules.
• The diatomic tungsten species is represented as W.
• Tungsten can form intercalation compounds with alkali metals, resulting in tungsten bronzes.
• An example of a tungsten bronze is sodium tungsten bronze.
• Tungsten bronzes are formed when tungsten compounds intercalate with alkali metals.
• Tungsten bronzes have unique properties and applications.
• Tungsten is part of many polyoxometalate anions.
• These anions exist as metastable species.
• Metatungstate is one example of a polyoxometalate anion.
• Metatungstate can be modified by replacing central hydrogens with different atoms like phosphorus.
• The substitution of atoms in metatungstate produces a variety of heteropoly acids.

Tungsten Data Sources