Tungsten

Tungsten, also known as wolfram, is a special kind of metal with the symbol W and atomic number 74. It was discovered in 1781 and first made into a metal in 1783. Tungsten is found in nature mostly mixed with other elements, in ores like scheelite and wolframite.

This metal is very strong and has the highest melting and boiling points of all known elements. It can stay solid at an amazing 3,422 °C and only turns into a gas at 5,930 °C. Tungsten is also very heavy, almost as heavy as uranium or gold.

Because of its strength and weight, tungsten is used in many important things like light bulb filaments, X-ray tubes, and strong alloys. It is also used to make very hard materials for cutting and drilling, and even in some military tools. Even though it is useful, tungsten can be harmful to many living things because it interferes with the way some metals work in our bodies.

Characteristics

Tungsten is a hard, steel-grey metal that can be difficult to shape. However, when purified, it becomes easier to work with and can be shaped through methods like forging or sintering. Sintering is often used because tungsten has an extremely high melting point.

Tungsten has the highest melting point of all metals, along with very low vapor pressure and high tensile strength. It does not change shape much when heated and keeps its strength even at high temperatures. This is because of the strong bonds between its atoms. Adding a small amount of tungsten to steel makes the steel stronger.

Tungsten naturally occurs with several stable forms and one very long-lasting radioactive form. Scientists have also created many artificial radioactive forms of tungsten, but they break down quickly.

Tungsten does not react with water, most acids, or air at normal temperatures. But when very hot, it reacts with oxygen. It can also react with fluorine, chlorine, bromine, and iodine under certain conditions. Tungsten combines with oxygen to form compounds, and with carbon to form very hard materials used in special tools. In water solutions, tungsten forms various ions and clusters, and in gas form, tungsten atoms connect with one of the strongest bonds known.

History

In 1781, a scientist named Carl Wilhelm Scheele discovered that a new acid, called tungstic acid, could be made from a mineral named scheelite. He and another scientist, Torbern Bergman, thought it might be possible to get a new metal from this acid. Two years later, in 1783, brothers José and Fausto Elhuyar found the same acid from another mineral called wolframite. They succeeded in isolating the metal tungsten by using charcoal, and they are credited with discovering the element. They called it "wolfram" or "volfram."

Tungsten became important in the early 20th century. During World War I and World War II, it was used in weapons and equipment because of its strong properties, like resistance to high temperatures and hardness. Tungsten is now used in many things, such as aircraft parts, sports equipment, and tools.

Etymology

The name "tungsten" means 'heavy stone' in Swedish and was used for minerals that are very dense. In many European languages, the element is called "wolfram," which comes from the mineral wolframite. The name "wolframite" comes from old German words meaning 'wolf soot' or 'wolf cream.' This name comes from a Latin phrase meaning 'wolf's froth,' because the mineral seemed to use up tin during extraction, as if a wolf was eating it. Miners often gave colorful names to minerals they thought were tricky or bad luck.

Occurrence

Tungsten is mainly found in minerals called wolframite and scheelite. Wolframite is a mix of iron and manganese combined with tungsten, while scheelite is calcium combined with tungsten. Pure tungsten has not been found naturally on Earth.

Chemical compounds

See also: Category:Tungsten compounds

Tungsten can form many different chemical compounds. Its oxidation states range from −2 to +6. Higher oxidation states, often found as oxides, are important for where tungsten is found on Earth and how it works in living things. Middle oxidation states are usually linked to groups of metal atoms, and very low oxidation states are often found with carbon monoxide compounds.

Tungsten and molybdenum have similar chemical behaviors, but they differ from chromium. One simple compound is tungsten(VI) oxide, WO₃, which is made of many linked parts. This oxide can dissolve in certain liquids, forming tungstate WO₄²⁻. At lower pH levels, it forms polyoxotungstates.

Tungsten also forms many different chlorides, such as:

• Tungsten(II) chloride, which exists as the hexamer W₆Cl₁₂
• Tungsten(III) chloride, which exists as the hexamer W₆Cl₁₈
• Tungsten(IV) chloride, WCl₄, a black solid with a chain-like structure
• Tungsten(V) chloride WCl₅, a black solid made of two linked parts
• Tungsten(VI) chloride WCl₆, which is different from the unstable MoCl₆

There are also many organotungsten compounds, including W(CH₃)₆ and W(CO)₆.

Production

Reserves

The world has about 3,200,000 tonnes of tungsten stored up, mostly in China, Canada, Russia, Vietnam, and Bolivia. China, Vietnam, and Russia are the top suppliers, providing 79,000, 7,200, and 3,100 tonnes each as of 2017. Canada stopped making tungsten in late 2015 when its only mine closed. Vietnam has grown a lot in making tungsten since the 2010s and now makes more than Russia and Bolivia.

China leads the world in making, selling, and using tungsten products. Tungsten making is growing outside of China because more people need it. China controls its tungsten closely to stop illegal mining and pollution.

There is a big tungsten deposit near Dartmoor in the United Kingdom. It was used during World War II at the Hemerdon Mine. The mine opened again in 2014 when tungsten prices went up but closed in 2018.

In the EU, the Felbertal area in Austria has one of the few tungsten mines that is still working. Portugal is a big tungsten maker in Europe.

Tungsten is sometimes called a conflict mineral because of unfair mining in the Democratic Republic of the Congo.

South Korea's Sangdong mine is one of the biggest tungsten mines in the world, with lots of tungsten inside. It closed in 1994 because it wasn’t making enough money but might open again in 2024.

Extraction

Tungsten is taken from its ores in steps. The ore is turned into tungsten(VI) oxide (WO₃). This is then heated with hydrogen or carbon to make powdered tungsten. Because tungsten melts at such a high temperature, it can’t be melted and shaped like other metals. Instead, the powder is mixed with a little nickel or other metals and heated to make a solid block.

Tungsten can also be made by using hydrogen on WF₆:

WF₆ + 3 H₂ → W + 6 HF

or by heating WF₆ on its own:

WF₆ → W + 3 F₂ (Δ_H__r = +)

Tungsten isn’t sold on big exchanges like the London Metal Exchange. Prices are set using independent groups like Argus Media or Metal Bulletin for tungsten concentrate or WO₃.

Applications

Tungsten is used in many important ways because of its special properties. About half of all tungsten is used to make very hard materials called tungsten carbide, which is one of the hardest substances known. This hard material is used to make tools that can cut through metal, wood, and other tough materials. It is also used in jewelry, where it makes very strong and long-lasting rings.

Tungsten is also used in alloys, which are mixtures of metals. These alloys are used in things like high-speed steel tools, rocket parts, and airplane engines. Because tungsten can handle very high temperatures, it is also used in welding rods and lighting filaments.

Biological role

Tungsten is the heaviest element known to help living things grow. Some tiny organisms, like certain bacteria and archaea, use tungsten in special helper molecules to do important jobs. These jobs include changing certain acids into different forms.

In soil, tungsten changes into a form that some tiny organisms can use. This can either help or stop these organisms from working properly, depending on the soil. Scientists have also studied how tungsten affects earthworms and found it can stop them from having babies.

Health factors

Tungsten is a rare metal found in very small amounts in the Earth's crust, about 1.5 parts per million. It is the 58th most common element on our planet.

Scientists once thought tungsten was not very harmful, but studies since the year 2000 have shown that certain forms of tungsten, like dust, might cause health problems for animals and humans. The amount that can be harmful depends on the type of test and the animal used.

People can come into contact with tungsten at work by breathing it in, swallowing it, or touching it with their skin or eyes. Special guidelines have been set to keep workplaces safe.