Difference between revisions of "Tungsten" - New World Encyclopedia
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* [http://www.vanderkrogt.net/elements/elem/w.html Elementymology & Elements Multidict by Peter van der Krogt - Tungsten] | * [http://www.vanderkrogt.net/elements/elem/w.html Elementymology & Elements Multidict by Peter van der Krogt - Tungsten] | ||
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Revision as of 22:32, 11 December 2005
- This article is about the chemical element. "Tungsten" may also refer to the Tungsten Handheld PDA or to the Tungsten pickups.
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Name, Symbol, Number | tungsten, W, 74 | ||||||||||||||||||||||||||||||||||||||||||||||||
Chemical series | transition metals | ||||||||||||||||||||||||||||||||||||||||||||||||
Group, Period, Block | 6, 6, d | ||||||||||||||||||||||||||||||||||||||||||||||||
Appearance | grayish white, lustrous | ||||||||||||||||||||||||||||||||||||||||||||||||
Atomic mass | 183.84(1) g/mol | ||||||||||||||||||||||||||||||||||||||||||||||||
Electron configuration | [Xe] 4f14 5d4 6s2 | ||||||||||||||||||||||||||||||||||||||||||||||||
Electrons per shell | 2, 8, 18, 32, 12, 2 | ||||||||||||||||||||||||||||||||||||||||||||||||
Physical properties | |||||||||||||||||||||||||||||||||||||||||||||||||
Phase | solid | ||||||||||||||||||||||||||||||||||||||||||||||||
Density (near r.t.) | 19.25 g/cm³ | ||||||||||||||||||||||||||||||||||||||||||||||||
Liquid density at m.p. | 17.6 g/cm³ | ||||||||||||||||||||||||||||||||||||||||||||||||
Melting point | 3695 K (3422 °C, 6192 °F) | ||||||||||||||||||||||||||||||||||||||||||||||||
Boiling point | 5828 K (5555 °C, 10031 °F) | ||||||||||||||||||||||||||||||||||||||||||||||||
Heat of fusion | 52.31 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||||||||
Heat of vaporization | 806.7 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||||||||
Heat capacity | (25 °C) 24.27 J/(mol·K) | ||||||||||||||||||||||||||||||||||||||||||||||||
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Atomic properties | |||||||||||||||||||||||||||||||||||||||||||||||||
Crystal structure | cubic body centered | ||||||||||||||||||||||||||||||||||||||||||||||||
Oxidation states | 6, 5, 4, 3, 2 (mildly acidic oxide) | ||||||||||||||||||||||||||||||||||||||||||||||||
Electronegativity | 2.36 (Pauling scale) | ||||||||||||||||||||||||||||||||||||||||||||||||
Ionization energies | 1st: 770 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||||||||
2nd: 1700 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||
Atomic radius | 135 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
Atomic radius (calc.) | 193 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
Covalent radius | 146 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
Miscellaneous | |||||||||||||||||||||||||||||||||||||||||||||||||
Magnetic ordering | no data | ||||||||||||||||||||||||||||||||||||||||||||||||
Electrical resistivity | (20 °C) 52.8 nΩ·m | ||||||||||||||||||||||||||||||||||||||||||||||||
Thermal conductivity | (300 K) 173 W/(m·K) | ||||||||||||||||||||||||||||||||||||||||||||||||
Thermal expansion | (25 °C) 4.5 µm/(m·K) | ||||||||||||||||||||||||||||||||||||||||||||||||
Speed of sound (thin rod) | (r.t.) (annealed) 4620 m/s | ||||||||||||||||||||||||||||||||||||||||||||||||
Speed of sound (thin rod) | (r.t.) 411 m/s | ||||||||||||||||||||||||||||||||||||||||||||||||
Shear modulus | 161 GPa | ||||||||||||||||||||||||||||||||||||||||||||||||
Bulk modulus | 310 GPa | ||||||||||||||||||||||||||||||||||||||||||||||||
Poisson ratio | 0.28 | ||||||||||||||||||||||||||||||||||||||||||||||||
Mohs hardness | 7.5 | ||||||||||||||||||||||||||||||||||||||||||||||||
Vickers hardness | 3430 MPa | ||||||||||||||||||||||||||||||||||||||||||||||||
Brinell hardness | 2570 MPa | ||||||||||||||||||||||||||||||||||||||||||||||||
CAS registry number | 7440-33-7 | ||||||||||||||||||||||||||||||||||||||||||||||||
Notable isotopes | |||||||||||||||||||||||||||||||||||||||||||||||||
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Tungsten (formerly wolfram) is a chemical element that has the symbol W (L. wolframium) and atomic number 74. A very hard, heavy, steel-gray to white transition metal, tungsten is found in several ores including wolframite and scheelite and is remarkable for its robust physical properties. The pure form is used mainly in electrical applications but its many compounds and alloys are widely used in many applications (most notably in light bulb filaments and in space-age superalloys).
Notable characteristics
Pure tungsten is steel-gray to tin-white and is a hard metal. Tungsten can be cut with a hacksaw when it is very pure (it is brittle and hard to work when impure) and is otherwise worked by forging, drawing, or extruding. This element has the highest melting point (3422 °C) (6192 °F) , lowest vapor pressure and the highest tensile strength at temperatures above 1650 °C (3000 °F) of all metals. Its corrosion resistance is excellent and it can only be attacked slightly by most mineral acids. Tungsten metal forms a protective oxide when exposed to air but can be oxidized at high temperature. When alloyed in small quantities with steel, it greatly increases its hardness.
Applications
Tungsten is a metal with a wide range of uses, the largest of which is as tungsten carbide (W2C, WC) in cemented carbides. Cemented carbides (also called hardmetals) are wear-resistant materials used by the metalworking, mining, petroleum and construction industries. Tungsten is widely used in light bulb and vacuum tube filaments, as well as electrodes, because it can be drawn into very thin metal wires that have a high melting point. Other uses;
- A high melting point also makes tungsten suitable for space-oriented and high temperature uses which include electrical, heating, and welding applications, notably in the GTAW process (also called TIG welding).
- Hardness and density properties make this metal ideal for making heavy metal alloys that are used in armaments, heat sinks, and high-density applications, such as weights, counterweights and ballast keels for yachts.
- The high density makes it an ideal ingredient for darts, normally 80% and sometimes up to 97%.
- High-speed tool steels (Hastelloy, Stellite) are often alloyed with tungsten, with tungsten steels containing as much as 18% tungsten.
- Superalloys containing this metal are used in turbine blades, tool steels, and wear-resistant alloy parts and coatings.
- Composites are used as a substitute for lead in bullets and shot.
- Tungsten chemical compounds are used in catalysts, inorganic pigments, and tungsten disulfide high-temperature lubricants which is stable to 500 °C (930 °F).
- Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals.
- It is used in kinetic energy penetrators, usually alloyed with nickel and iron or cobalt to form tungsten heavy alloys, as an alternative to depleted uranium.
Miscellaneous: Oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting. Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine. The metal is also used in X-ray targets and heating elements for electrical furnaces. Salts that contain tungsten are used in the chemical and tanning industries. Tungsten 'bronzes' (so-called due to the colour of the tungsten oxides) along with other compounds are used in paints. Tungsten Carbide has recently been used in the fashioning of jewelry due to its hypoallergenic nature and the fact that due to its extreme hardness it is not apt to lose its luster like other polished metals.
History
Tungsten (Swedish and Danish tung sten meaning "heavy stone", even though the current name for the element in Swedish is Wolfram) was first hypothesized to exist by Peter Woulfe in 1779 who examined wolframite and concluded that it must contain a new substance. In 1781 Carl Wilhelm Scheele ascertained that a new acid could be made from tungstenite. Scheele and Torbern Bergman suggested that it could be possible to obtain a new metal by reducing tungstic acid. In 1783 José and Fausto Elhuyar found an acid in wolframite that was identical to tungstic acid. In Spain later that year the brothers succeeded in isolating tungsten through reduction of this acid with charcoal. They are credited with the discovery of the element.
In World War II, tungsten played an enormous role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its sources of wolframite ore. The resistance to high temperatures, as well as the extreme strength of its alloys, made the metal into a very important raw material for the weaponry industry.
Biological role
Enzymes called oxidoreductases use tungsten in a way that is similar to molybdenum by using it in a tungsten-pterin complex.
On August 20, 2002 officials representing the U.S.-based Centers for Disease Control and Prevention announced that urine tests on leukemia patient families and control group families in the Fallon, Nevada area had shown elevated levels of the metal tungsten in the bodies of both groups. 16 recent cases of cancer in children were discovered in the Fallon area which has now been identified as a "Cancer Cluster." Dr. Carol H. Rubin, a branch chief at the CDC, said data demonstrating a link between tungsten and leukemia is not available at present.
Occurrence
Tungsten is found in the minerals wolframite (iron-manganese tungstate, FeWO4/MnWO4), scheelite (calcium tungstate, CaWO4), ferberite and huebnerite. Important deposits of these minerals are in Bolivia, California, China, Colorado, Portugal, Russia, and South Korea (with China producing about 75% of the world's supply). The metal is commercially produced by reducing tungsten oxide with hydrogen or carbon.
Compounds
The most common oxidation state of tungsten is +6, but it exhibits all oxidation states from +2 to +6. Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO42−.
Aqueous polyoxoanions
Aqueous tungstate solutions are noted for the formation of polyoxoanions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion, W7O246−, which over hours or days converts to the less soluble "paratungstate B" anion, H2W12O4210−. Further acidification produces the very soluble metatungstate anion, H2W12O406−, after equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the "Keggin" anion. Many other polyoxoanions exist as metastable species. The inclusion of a different atom such as phosphorus in place of the two central hydrogens in metatungstate produces a wide variety of the so-called heteropolyanions.
Isotopes
Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable. All can decay into isotopes of element 72 (hafnium) by alpha emission. Alpha decay has only been observed, in 2003, in the lightest and rarest of them, 180W. On average, two alpha decays of 180W occur in one gram of natural tungsten per year.
27 artificial radioisotopes of tungsten have been characterized, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days and 178W with a half-life of 21.6 days. All of the remaining radioactive isotopes have half-lives of less than 24 hours, and most of these have half-lives that are less than 8 minutes. Tungsten also has 4 meta states, the most stable being 179mW (t½ 6.4 minutes).
ReferencesISBN links support NWE through referral fees
External links
- WebElements.com - Tungsten
- ScienceLab.com - Tungsten
- picture in the collection from Heinrich Pniok
- Tungsten-Scrap.com - Articles about Tungsten and applications for Tungsten scrap
- Elementymology & Elements Multidict by Peter van der Krogt - Tungsten
ar:تنجستن
ca:Tungstè
cs:Wolfram
da:Wolfram
de:Wolfram
et:Volfram
es:Wolframio
eo:Volframo
fr:Tungstène
is:Volfram
it:Tungsteno
he:טונגסטן
ku:Tûngsten
lt:Volframas
lv:Volframs
hu:Volfrám
nl:Wolfraam
ja:タングステン
no:Wolfram
nn:Wolfram
pl:Wolfram (pierwiastek)
pt:Tungstênio
ru:Вольфрам
sl:Volfram
sr:Волфрам
fi:Volframi
sv:Volfram
th:ทังสเตน
uk:Вольфрам
zh:钨
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