Tungsten
Contents
Background
Tungsten is a gray-white metallic element. Its atomic number is 74 and its atomic symbol is W (after the German name Wolfram given to this element). It is stable and is very resistant to acids and bases. It does, however, oxidize in air (Atmospheric composition and structure), especially at higher temperatures. It has the highest melting temperature of any metal (3,422 degrees Celsius, 6,192 degrees Fahrenheit), and the second highest of all elements (Carbon is highest).
Tungsten was discovered in 1758 by Axel Fredrik Cronstadt; in 1781 Carl Wilhelm Scheele isoldated a tungsten oxide, and in 1783 the Spanish chemists (and brothers) Fausto and Juan Jose de Elhuyar first separated tungsten from the mineral wolframite.
It is interesting to note that tungsten is important to the health of plants and animals. Specifically, it is used by some enzymes (which are called oxidoreductases).
Name
| Previous Element: Tantalum Next Element: Rhenium |
| |
| Physical Properties | ||
|---|---|---|
| Color | bluish-gray | |
| Phase at Room Temp. | solid | |
| Density (g/cm3) | 19.3 | |
| Hardness (Mohs) | --- | |
|
Melting Point (K) |
3683.2 | |
|
Boiling Point (K) |
5773 | |
| Heat of Fusion (kJ/mol) | 35.229 | |
| Heat of Vaporization (kJ/mol) | 824 | |
| Heat of Atomization (kJ/mol) | 849 | |
| Thermal Conductivity (J/m sec K) | 173 | |
| Electrical Conductivity (1/mohm cm) | 176.991 | |
| Source | Scheelite, Wolframite (oxide) | |
| Atomic Properties | ||
| Electron Configuration | [Xe]6s24f145d4 | |
|
Number of Isotopes |
36 (5 natural) | |
| Electron Affinity (kJ/mol) | 78.6 | |
| First Ionization Energy (kJ/mol) | 770 | |
| Second Ionization Energy (kJ/mol) | --- | |
| Third Ionization Energy (kJ/mol) | --- | |
| Electronegativity | 2.36 | |
| Polarizability (Å3) | 11.1 | |
| Atomic Weight | 183.85 | |
| Atomic Volume (cm3/mol) | 9.5 | |
| Ionic Radius2- (pm) | --- | |
| Ionic Radius1- (pm) | --- | |
| Atomic Radius (pm) | 139 | |
| Ionic Radius1+ (pm) | --- | |
| Ionic Radius2+ (pm) | --- | |
| Ionic Radius3+ (pm) | --- | |
| Common Oxidation Numbers | +4, +6 | |
| Other Oxid. Numbers | -2, -1, +1, +2, +3, +5 | |
| Abundance | ||
| In Earth's Crust (mg/kg) | 1.25x100 | |
| In Earth's Ocean (mg/L) | 1.0x10-4 | |
| In Human Body (%) | 0% | |
| Regulatory / Health | ||
| CAS Number | 7440-33-7 | |
| OSHA Permissible Exposure Limit (PEL) | No limits | |
| OSHA PEL Vacated 1989 | TWA: 5 mg/m3 STEL: 10 mg/m3 | |
|
NIOSH Recommended Exposure Limit (REL) |
TWA: 5 mg/m3 STEL: 10 mg/m3 | |
|
Sources: |
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Tungsten was named from the Swedish words "tung sten" meaning "heavy stone."
Sources
Tungsten is retrieved from the ore minerals scheelite (CaWO4, calcium tungstate) and wolframite ((Fe,Mn)WO4, iron-manganese tungstate). Of the world’s tungsten reserves, over 90% are outside the United States. Of these resources (Natural resource quality), nearly half are found in China, and Canada and Russia also have large reserves. About one-third of the U.S. imports of tungsten are from China, Russia provides about 25%, and a variety of other nations provide the rest. A significant amount of tungsten is recovered through recycling of scrap tungsten products. Recycled tungsten in the U.S. accounts for nearly one-third of the tungsten consumed. Major production of tungsten concentrates come from Austria, Bolivia, Canada, China, Portugal, and Russia.
Uses
Tungsten is mixed with carbon to make a very strong, very resistant material called tungsten carbide. Tungsten carbide is used to make cutting tools and wear-resistant tools for metalworking, drilling for oil and gas, mining, and construction. These applications account for more than 60% of the tungsten consumed in the U.S. each year.
Because it has such a very high melting point and low vapor pressure, tungsten is used in high temperature situations. For instance, the filaments in light bulbs are made of tungsten. It is used in other applications in electronics as well.
When added to steel, tungsten increases its strength. It is alloyed (mixed with) other metals to make "superalloys" which have special physical properties of high strength and heat resistance. Some of the applications for such superalloys are in turbine engines for jet aircraft and energy generation.
Other alloys bearing tungsten are used for armaments, heat sinks, radiation shielding, weights and counterweights, wear-resistant parts and coatings.
Substitutes and Alternative Sources
Tungsten is the only material used to make light bulb filaments. Experiments are being done with ceramic and ceramics mixed with metals to create alternative cutting materials. Cemented carbide made with tungsten carbide is still preferred to these materials.
Further Reading
- Common Minerals and Their Uses, Mineral Information Institute.
- More than 170 Mineral Photographs, Mineral Information Institute.
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