Tungsten Facts – W or Atomic Number 74 (Wolfram)


Tungsten Facts

Tungsten is a chemical element with the symbol W and atomic number 74 that stands out for its remarkable properties, especially its extreme melting point. The name ‘tungsten’ comes from the Swedish words “tung sten”, meaning “heavy stone”. Its chemical symbol, W, derives from its earlier name, wolfram, which remains in use in some countries.

Discovery

In 1781, Swedish chemist Carl Wilhelm Scheele found that a new acid, tungstic acid, could be made from scheelite ore. Scheel and Torbern Bergman proposed that reducing this acid might yield a new metal. In 1783, Spanish brothers Juan José and Fausto Elhuyar isolated tungsten in its pure form for the first time by reducing tungstic acid using charcoal. Thus, the Elhuyar brothers get official credit for discovering and isolating the element, which they called “wolfram” or “volfram.”

Tungsten Name and Symbol

The usage of the name “wolfram” or “tungsten” is primarily a matter of linguistic and historical tradition. The International Union of Pure and Applied Chemistry (IUPAC) officially recognizes “tungsten” as the name of the element and the symbol ‘W’ (derived from “wolfram”). This serves as a nod to the element’s history and the varied linguistic backgrounds of the scientific community.

The name “wolfram” predominates in several European countries, including Germany, Austria, and Portugal. The name “wolfram” derives from the mineral wolframite, from which tungsten was first extracted. The term “wolframite,” in turn, comes from “wolf rahm,” a phrase used by German miners. It referred to the tin-consuming properties of the mineral, as “wolf cream” (wolf rahm) metaphorically devoured the tin like a wolf.

On the other hand, the name “tungsten” is common in English-speaking countries and comes from Swedish, where “tung sten” literally means “heavy stone.” The element’s high density likely inspired the name, emphasizing its notable physical characteristic of being exceptionally heavy. The Swedish chemist Carl Wilhelm Scheele, who first identified the acid in tungstic ore, was influential in the adoption of this name. Initially, the symbol accompanying the name tungsten was Tn.

Element Group

Tungsten belongs to Group 6 in the periodic table, along with chromium and molybdenum. It is a transition metal and a refractory metal. Like other Group 6 elements, tungsten forms compounds in multiple oxidation states and displays a strong resistance to heat.

Appearance and Properties

Tungsten is a hard, steel-gray to white metal that is brittle at lower temperatures but ductile and malleable upon heating. It has the highest melting point of all metals and the second highest of all elements after carbon. It has the highest tensile strength, lowest coefficient of thermal expansion, and lowest vapor pressure of the elements. This metal has a high density, just less than gold’s.

Chemically, tungsten displays low reactivity. It does not react with water or oxygen at room temperature and resists attack by most acids and bases. It does react with fluorine at room temperature and with other halogens at elevated temperatures. Finely powdered tungsten is pyrophoric.

Oxidation States and Main States

Electron Levels of a Tungsten Atom

Tungsten exhibits several oxidation states, ranging from -4 to +6. The most common and stable state is +6, seen in compounds like tungsten trioxide (WO3). The +4 oxidation state is also common and stable.

Tungsten Allotropes

The two major crystalline forms or allotropes of tungsten are α and β. The alpha form is more stable and has a body-centered cubic structure. The beta phase is metastable and has the A15 cubic crystal structure. While the alpha phase crystallizes into isometric grains, the beta phase forms columns.

Natural and Radioactive Isotopes

Natural tungsten consists of four stable isotopes (182W, 183W, 184W, and 186W) and one long-lived radioisotope (180W). At least 34 synthetic radioisotopes are known. The most stable of these is 181W, with a half-life of 121.2 days.

Abundance and Sources

Tungsten is a rare metal that has an abundance of around 1.5 parts per million in the Earth’s crust. This element occurs in several ores, including wolframite and scheelite. There are major ore deposits in China, Russia, and Portugal.

Purification

The purification of tungsten involves crushing the ore and then using physical and chemical processes to remove impurities. The main steps include flotation to concentrate the ore, followed by roasting and chemical treatment to extract tungsten trioxide. Reducing tungsten trioxide using hydrogen or carbon yields metallic tungsten.

Uses of Tungsten

Tungsten has a wide range of applications due to its unique properties:

  • As a filament in light bulbs and in electronics due to its high melting point.
  • In alloys, such as high-speed steel, to increase hardness and durability.
  • In military applications for its density and hardness, including in kinetic energy penetrators.
  • In jewelry, often alloyed with other metals for its attractive appearance and durability.
  • As electrodes in welding, thanks to its high melting point and conductivity.
  • In permanent magnets as quenched tungsten steel, where tungsten (which is not magnetic) stabilizes the martensite phase of iron and improves the steel’s ferromagnetism.
  • As a high-temperature lubricant in the form of tungsten(IV) sulfide.
  • As catalysts in the chemical industry, for example, in the hydrocracking process where they help break down large hydrocarbon molecules in crude oil.

Biological Role, Health Effects, and Toxicity

  • Humans: Tungsten has no known biological role in humans. Tungsten interferes with metabolic processes that use molybdenum. While the pure element exhibits low toxicity, certain tungsten compounds are potentially harmful if ingested or inhaled. Chronic exposure causes lung and bone issues. Also, tungsten and its compounds are potentially carcinogenic.
  • Wildlife: Animals exposed to high levels of tungsten, such as near industrial sites, experience similar health effects as humans.
  • Microorganisms: In some bacteria and archaea, tungsten is a component of enzymes. These tungsten-dependent enzymes involve processes like the reduction of carboxylic acids. They are analogous to more common molybdenum-dependent enzymes but function in extreme environments where molybdenum might be scarce.
  • Plants: While tungsten is not known to play a biological role in plants, studies indicate that high concentrations are toxic, leading to reduced growth and photosynthesis. However, some plants accumulate tungsten without apparent harm, suggesting a degree of tolerance or potential mechanisms of detoxification.
  • Aquatic Life: Tungsten compounds can be toxic to fish and other aquatic organisms. The toxicity depends on the specific form of tungsten and the environmental conditions.

Table of Key Tungsten Facts

Tungsten’s key properties include low toxicity and high melting point, density, and hardness.

PropertyTungsten Facts
NameTungsten
SymbolW
Atomic Number74
Atomic Weight183.84
Group6
Period6
Blockd-block
Electron Configuration[Xe] 4f14 5d4 6s2
Electrons Per Shell2, 8, 18, 32, 12, 2
State at Room TemperatureSolid
Melting Point3422°C
Boiling Point5930°C
Density19.25 g/cm^3
Heat of Fusion52.31 kJ/mol
Heat of Vaporization774 kJ/mol
Molar Heat Capacity24.27 J/(mol·K)
Oxidation States-4, -2, -1, 0, +1, +2, +3, +4, +5, +6
Electronegativity2.36 (Pauling scale)
Ionization Energies1st: 770 kJ/mol, 2nd: 1700 kJ/mol
Atomic Radius139 pm
Covalent Radius162 pm
Crystal StructuresBody-centered cubic (bcc)
Thermal Conductivity173 W/(m·K)
Electrical Resistivity5.6 × 10−8 Ω·m
Young’s Modulus411 GPa
Shear Modulus161 GPa
Bulk Modulus310 GPa
Mohs Hardness7.5
Magnetic OrderingParamagnetic

Interesting Tungsten Facts

Here are some interesting and unusual facts about tungsten:

  • Incandescent Light Bulb Filament Discovery: Tungsten revolutionized the lighting industry. The first person to use tungsten as a filament in light bulbs was William David Coolidge in 1903. His development of the ductile form of tungsten made it possible to use in light bulbs, leading to longer-lasting and more efficient bulbs.
  • Firearm Projectiles: Tungsten is used in some firearm projectiles as an alternative to lead, offering higher density and hardness. This helps projectiles maintain velocity over longer distances.
  • Counterfeit Gold Bars: Due to its similar density to gold, tungsten has been used in counterfeit gold bars. It’s difficult to distinguish between gold and tungsten by simply weighing the bars.
  • Tungsten Rings: Tungsten carbide rings are popular in jewelry for their extreme hardness and resistance to scratching. They are especially favored as wedding bands for their durability and unique metallic luster.
  • Superalloy Component: Tungsten is a key component in superalloys, which are used in jet engines and turbines. These alloys can withstand extreme temperatures while maintaining strength and stability.
  • Spacecraft Shielding: The high density of tungsten makes it suitable for radiation shielding in spacecraft and as counterweights for space telescopes.
  • Diamond Substitute: Polycrystalline tungsten carbide is so hard that it is often used in place of diamond in abrasives and cutting tools.
  • Historical Confusion with Lead: Tungsten was historically confused with lead. Its ore, wolframite, interfered with tin smelting, and it was initially thought to contain lead.
  • Role in Climbing Plants: Some climbing plants use tungsten in their root systems to help them climb and support themselves.
  • Tungsten Boiling Point Anomaly: Despite having the highest melting point of all metals, tungsten does not have the highest boiling point. That distinction belongs to rhenium.
  • Superconductivity: Under certain conditions, tungsten becomes superconductive. However, this occurs at extremely low temperatures, far colder than the temperatures required for most other superconductors.

References

  • Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  • Hille, Russ (2002). “Molybdenum and tungsten in biology”. Trends in Biochemical Sciences. 27 (7): 360–367. doi:10.1016/S0968-0004(02)02107-2
  • Lassner, Erik; Schubert, Wolf-Dieter (1999). Tungsten: Properties, Chemistry, Technology of the Element, Alloys, and Chemical Compounds. Springer. ISBN 978-0-306-45053-2.
  • Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. ISBN 978-0-8493-0464-4.