The Tough Element Tungsten

tungsten element image

Introduction to Tungsten

The element tungsten is a silvery gray transition metal. Tungsten is known for having a remarkably high melting point and incredible tensile strength compared to other pure metals. Because of these qualities, we often use tungsten to produce industrial equipment and tools.

10 Fun Facts about Tungsten

  • Tungsten has remarkably high radiation resistance.
  • Compared with all other metals, tungsten is the second hardest after chromium.
  • Tungsten has the highest melting point (3422°C) of any other element on the periodic table.
  • Tungsten is remarkably dense. It has a density just slightly higher than gold, and the 5th highest density of all transition metals.
  • When exposed to oxygen, an oxide layer develops on the surface of tungsten crystals, which can have a rainbow color similar to bismuth.
  • Tungsten is one of two elements that are theoretically capable of forming sextuple bonds. Specifically, these bonds exist in W2, the diatomic gaseous form of tungsten, which only forms beyond its boiling point of 5930°C. This bond involves two sigma, two pi, and two delta bonds, and is only possible due to the unique configuration of tungsten’s electrons.
  • The name “tungsten” means “heavy stone” in Swedish, and the name originally served as the Swedish term for the mineral scheelite, an ore that includes tungsten.
  • Its symbol on the periodic table, W, doesn’t refer to the name “tungsten,” but rather the name “wolfram”. In German, Spanish, and many Slavic languages, “wolfram” is the name of the element, while “tungsten” is instead used by English and French speakers.
  • When inside most organisms, tungsten can have toxic effects. Specifically, tungsten can replace molybdenum or copper cofactors in certain enzyme-catalyzed reactions.
  • Interestingly, some species of bacteria have developed a use for tungsten in catalyzing certain redox reactions.

Tungsten in the Periodic Table

Tungsten has the atomic symbol W with an atomic number of 74. It locates in the d-block of the periodic table, with tantalum to its left and rhenium to its right. Tungsten occupies the third element in Group 6 of the periodic table, with chromium, molybdenum, and seaborgium. Tungsten has an electron configuration of [Xe]4f145d46s2. Additionally, the element has an electronegativity of 2.36 on the Pauling scale. 

Tungsten in Warfare

Due to its remarkable tensile strength (1510MPa), high melting point (3422°C), and corrosion resistance, tungsten served as an important component of heavy weaponry in the early 20th century. With tungsten-enriched alloy, factories could make weaponry that could withstand larger internal blasts to shoot larger payloads over longer distances. 

Specifically, during the First World War, the demand of the European Great Powers to build artillery made tungsten incredibly expensive. Tungsten sold at a higher per-mass price than gold or silver. Because it remained neutral for much of the war, both sides of the conflict looked to the US to buy tungsten. Many US tungsten mines existed in the American West, and their adjacent rural towns became incredibly busy and wealthy. However, after the war, the price for tungsten dropped, leaving behind eventual ghost towns, such as Tungsten, Colorado.

During the Second World War, the demand for tungsten skyrocketed once again. The British Empire blocked the trade of war material with Nazi Germany, including tungsten ore. This trade embargo extended to the rest of the Allied Powers, as well as having neutral signatories, including Portugal. At the time, Portugal had a repressive military dictatorship, under the leadership of Antonio de Oliveira Salazar. However, Salazar had sympathies toward Nazi Germany, though wanted to maintain relations with Great Britain. Upon receiving generous sums from Germany, Salazar covertly traded tungsten ore from Northern Portugal with Germany. Portuguese ore inevitably helped build the weapons that Nazi Germany used to wage war, serving as Portugal’s enduring legacy during World War 2.

Tungsten’s Application in Today’s World

What is tungsten used for?

As mentioned before, tungsten’s utility in the modern world comes from its remarkable tensile strength and melting point. Tungsten can often be found in wires, bars, and high-stress tools used in industry. Common tungsten-rich tools include saws, drills, and mining equipment. Additionally, tungsten filaments and electrodes have considerable use in electronics, such as in lightbulbs and television displays. Tungsten ions can also be used in novel methods of chemical catalysis and synthesis.

Tungsten alloys have a lot of unique qualities that make them perfect for a whole host of applications. (See below).

Where is tungsten found?

Tungsten is a rather rare metal when found naturally on Earth. Generally, the metal occurs as a component in the minerals scheelite and wolframite. In both of these ores, tungsten occurs within the ion tungstate (WO42-). In wolframite, tungstate ionically bonds with iron and magnesium cations, while in scheelite, tungstate bonds with calcium cations. Other minerals with tungsten tend to be very rare.

tungsten element in scheelite
Scheelite, a common tungsten ore

The majority of the world’s tungsten reserves are located in China, though Canada, Russia, Vietnam, Bolivia, and Portugal also have significant tungsten deposits.

When and How was the Element Tungsten Discovered?

Historians now recognize that Carl Wilhelm Scheel, a Swedish chemist, discovered “tungstic acid” from an ore called “tungsten” in 1781. This ore later received the name “scheelite,” after the chemist. The name “tungsten” applied specifically to the new element once it was isolated from Scheele’s acid substance.

However, in 1783, two Spanish chemists (who were also brothers) named Fausto and José Elhuyar discovered the same acid substance from wolframite. Once the element isolated from the acid, the element went by the name “wolfram”. Spanish authorities credited the brothers with the discovery of the new element, and Scheele received credit for his discovery much later. Because of its troubled discovery, tungsten still retains “W” as its atomic symbol. 

Tungsten Element Chemistry – Compounds, Reactions, Oxidation States

Tungsten Element Alloys

Material scientists have made numerous useful alloys with tungsten, including:

  • Tungsten-Nickel-Iron: This alloy retains the strength and melting point of tungsten, and also has a low heat expansion coefficient. Low expansion makes this allow perfect for glass-to-metal sealing. Additionally, it has higher radiation shielding than lead while not being toxic to biological systems, making it perfect for radiation protection.
  • Tungsten-Iron-Carbon: This alloy has the advantage of withstanding incredibly high temperatures without losing hardness. As a result, metallurgists use it primarily in power-saw blades and drill bits, items that experience lots of friction at high speeds. Due to its advantageous qualities in high-speed friction, metallurgists call this allow “High-Speed Steel”.
  • Tungsten Nickel-Copper: This alloy has many qualities of Tungsten-Nickel-Iron, in addition to being highly conductive of electricity and non-magnetic. This makes the alloy perfect for high-tech electrical equipment, including military and medical technology.
  • Tungsten-Tantalum: This alloy also has a high melting point, in addition to having high tension and corrosion resistance. As a result, it tends to serve well in high-corrosion environments, like in spacecraft, nuclear plants, and furnaces.

Tungsten Element Compounds and Reactions

Notable tungsten compounds include:

  • Tungsten Carbides (WC, W2C): This compound has high hardness and stiffness, and is often used in industrial tools as well as jewelry.
tungsten carbide
Ball and stick model of WC crystal
  • Tungsten Halides (WF6, WCl6, W6Cl18, etc): These compounds form with relative ease from elemental tungsten. Chemists tend to use them to make more valuable tungsten compounds.
W6Cl18 model
Ball-and-stick model of W6Cl18

Tungstate Anion (WO42-): This is the most common free ionic form of tungsten. It’s also the predominant form found in nature, paired with a cation of another metal.

tungstate anion
Tungstate anion

Tungsten Hexacarbonyl (W(CO)6): This tungsten complex involves six carbon monoxide ligands interacting with tungsten. This compound has importance as a precursor to the first synthesized dihydrogen complex, which involves intact H2 as a ligand.

tungsten hexacarbonyl
Tungsten Hexacarbonyl Complex

Chemists have found that tungsten tends to have little reactivity under most conditions. However, a pair of useful reactions involving elemental tungsten have been discovered:

  • Halogenation: This involves reacting elemental tungsten with a diatomic halogen. This can happen at room temperature with F2 but requires significant heat (250°C) to react with Cl2. The result is a tungsten halide. This reaction has importance because tungsten halides can react to form tungsten carbide or tungsten complex salts.

W + 3F2 → WF6

W + 3Cl2 → WCl6

6W + 6Cl2 → W6Cl12

  • Reaction with Oxygen: This involves reacting elemental tungsten with diatomic oxygen, forming tungsten trioxide (WO3). Like with chlorine, this requires high temperatures. Under basic conditions, the tungsten trioxide forms tungstate (WO42-).

2W + 3O2 → WO3

Isolation of Tungsten Element

As mentioned before, tungsten naturally occurs in the form of metal (II) tungstates (FeWO4, MgWO4, CaWO4). To extract the elemental tungsten from ore, the tungstate compound converts to tungsten (IV) oxide (WO3). This product is then heated to produce powdered elemental tungsten.

Tungsten Element Oxidation States

Tungsten’s oxidation states include:

  • Tungsten(II): W2+, W2C
  • Tungsten(III): W3+, W6Cl18
  • Tungsten(IV): W4+, WC
  • Tungsten(V): W5+, WCl5
  • Tungsten(VI): W6+, WO42-, WO3

Properties of Tungsten Element

  • Atomic Symbol: W
  • Melting point: 3695K; 3422°C; 6192°F
  • Boiling point: 6203K; 5930°C; 10706°F
  • Density: 19.26 g/ml
  • Atomic weight: 183.84
  • Atomic number: 74
  • Electronegativity: 2.36
  • Molar heat capacity: 24.27 J/(mol*K)
  • Classification: Transition Metal
  • Natural abundance in the Earth’s crust: 1.5 ppm
  • Electron shell configuration: [Xe]4f145d46s2
  • Stable Isotopes: 180, 181, 182, 183, 184, 186
  • Found naturally in the minerals: Wolframite, scheelite, ferberite, hübnerite
  • Toxicity: Moderately toxic

Where Can I Buy Tungsten?

Vendors of most other metals also sell tungsten, often in the form of tungsten carbide or some alloy. Online vendors also have elemental tungsten for sale at prices as low as $2 per gram.

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