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'''Tungsten''' ({{pronEng|ˈtʌŋstən}}), also known as '''wolfram''' ({{IPA|/ˈwʊlfrəm/}}), is a ] that has the symbol '''W''' and ] 74.

sten have been characterized, the most stable of which are <sup>181</sup>W with a ] of 121.2&nbsp;days, <sup>185</sup>W with a half-life of 75.1&nbsp;days, <sup>188</sup>W with a half-life of 69.4&nbsp;days, <sup>178</sup>W with a half-life of 21.6&nbsp;days, and <sup>187</sup>W with a half-life of 23.72 h.<ref name=isotopes/> All of the remaining ] isotopes have half-lives of less than 3&nbsp;hours, and most of these have half-lives that are less than 8&nbsp;minutes.<ref name=isotopes/> Tungsten also has 4&nbsp;]s, the most stable being <sup>179m</sup>W (''T''<sub>½</sub> 6.4&nbsp;minutes).

==Chemical properties==
Elemental tungsten resists attack by ], ]s, and ]s.<ref name = "emsley"/>

===Compounds===
:<div class="noprint relarticle mainarticle">''Main article: ]

The most common formal ] of tungsten is +6, but it exhibits all oxidation states from -1 to +6.<ref name="emsley">Emsley, John E. <u>The elements</u>. 2nd ed. New York: Oxford University Press, 1991</ref> Tungsten typically combines with oxygen to form the yellow ], WO<sub>3</sub>, which dissolves in aqueous alkaline solutions to form tungstate ions, WO<sub>4</sub><sup>2&minus;</sup>.

]s (W<sub>2</sub>] and WC) are produced by heating powdered tungsten with ] and are some of the hardest ]s, with a melting point of 2770&nbsp;°C for WC and 2780&nbsp;degrees C for W<sub>2</sub>C. WC is an efficient ], but W<sub>2</sub>C is not as efficient. Tungsten carbide behaves in a manner very similar to that of unalloyed tungsten and is resistant to chemical attack, although it reacts strongly with ] to form ] (WCl<sub>6</sub>).<ref name="daintith"/>

====Aqueous polyoxoanions====
Aqueous tungstate solutions are noted for the formation of heteropoly acids and ] ]s under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, ] "paratungstate A" ], {{chem|W|7|O|24|<sup>6&minus;</sup>}}, which over hours or days converts to the less soluble "paratungstate B" anion, {{chem|H|2|W|12|O|42|<sup>10&minus;</sup>}}.<ref name="SmithBJ">{{cite journal|last=Smith|first=Bradley J.|year=2000|title=Quantitative Determination of Sodium Metatungstate Speciation by 183W N.M.R. Spectroscopy |journal=Australian Journal of Chemistry|publisher=CSIRO|volume=53|issue=12|url=http://www.publish.csiro.au/paper/CH00140.htm|accessdate=2008-06-17}}</ref> Further acidification produces the very soluble metatungstate anion, {{chem|H|2|W|12|O|40|<sup>6&minus;</sup>}}, after equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-] ] known as the "Keggin" anion. Many other polyoxometalate anions exist as metastable species. The inclusion of a different atom such as ] in place of the two central ]s in metatungstate produces a wide variety of ]s, such as ] H<sub>3</sub>P W<sub>12</sub>O<sub>40</sub> in this example.

==Biological role==
Tungsten is an ] for some organisms. For example, ]s called ]s use tungsten in a way that is similar to ] by using it in a tungsten-] complex.<ref name="tungsten_orgs">{{cite book|last=Lassner|first=Erik|title=Tungsten: Properties, Chemistry, Technology of the Element, Alloys and Chemical Compounds|publisher=Springer|year=1999|pages=409-411|isbn=0306450534|url=http://books.google.com/books?id=foLRISkt9gcC&pg=PA409&lpg=PA409&dq=tungsten+nutrient+organisms&source=web&ots=-rtHF9sWBY&sig=CoCD7Wp0HS-QRzQEoiPCisLaP04&hl=en&sa=X&oi=book_result&resnum=1&ct=result}}</ref>

On ], ], officials representing the U.S.-based ] announced that ] tests on ] patient families and control group families in the ] area had shown elevated levels of tungsten in the bodies of both groups.<ref>{{cite web
| url = http://www.cdc.gov/nceh/clusters/Fallon/study.htm
| publisher = Centers for Disease Control and Prevention
| title = Cross-Sectional Exposure Assessment of Environmental Contaminants in Churchill County, Nevada
| date = 2003-02-06
| accessdate = 2008-05-09 }}</ref> Sixteen recent cases of ] in children were discovered in the Fallon area, which has now been identified as a ]; although the majority of the cancer victims are not longtime residents of Fallon. However, there is not enough data to support a link between tungsten and leukemia at this time.<ref name="MullenFrankX">{{cite web |url = http://www.familiesagainstcancer.org/?id=344 | publisher = Reno Gazette-Journal | last = Mullen | first = Frank X. | title = Mouse Study Findings key in Fallon Cancer Cases, Scientists Say | date = ], ] | accessdate = 2008-06-17}}</ref>

==Applications==
].]]
Because of its ability to produce hardness at high temperatures and its high ] (the second highest of any known element), elemental tungsten is used in many high-temperature applications.<ref>DeGarmo, E. Paul. <u>Materials and Processes in Manufacturing</u>. 5th ed. New York, New York: MacMillan Publishing, 1979.</ref> These include ], ], and ] filaments, as well as ]s and nozzles on ]s.<ref name="albert"/> The high melting point also makes tungsten suitable for aerospace and high temperature uses which include electrical, heating, and welding applications, notably in the ] process (also called ] welding).

Due to its conductive properties, as well as its relative chemical inertia, tungsten is also used in ]s, and in the emitter tips of ] electron-beam instruments, such as ] (FIB) and ]s. In electronics, tungsten is used as an interconnect material in ]s, between the ] ] material and the transistors. Additionally, it is used in the manufacture of metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (or ]) on ].<ref name="manny">Schey, John A. <u>Introduction to Manufacturing Processes.</u> 2nd ed. McGraw-Hill, Inc, 1987.</ref>

In ], steel was put under restricted commercial uses, so Victor developed a tungsten gramophone needle. Called the "Tungs-tone" stylus (as Victor called it), this needle could withstand about 50 to 100 uses before wearing out the record. Victor claimed the needle could be used 300 times, but this would likely cause excessive wear/damage to a record. Victor stated that the needle be tested in the run-off (near the label) grooves and be rotated a quarter turn periodically, and then be tested in the run-off grooves. Victor stated that a Tungs-tone should be a used one for playing a record.<ref> name="Tungs-tone">{{cite web|url=http://www.gracyk.com/needletips.shtml}}</ref>

The electronic structure of tungsten makes it one of the main sources for ] targets,<ref name="patent">{{cite web|url=http://www.patentstorm.us/patents/6428904/description.html|title=US Patent 6428904 - X-ray target|date=], ]|publisher=|accessdate=2008-06-18}}</ref> and also for shielding from high-energy radiations (such as in the ] industry for shielding radioactive samples of ]). Tungsten powder is used as a filler material in ] composites, which are used as a nontoxic substitute for ] in ]s, shot, and radiation shields. Since this element's thermal expansion is similar to ], it is used for making glass-to-metal seals.<ref name="desu"/>

The hardness and density of tungsten are applied in obtaining ] ]s. A good example is ], which may contain as much as 18% tungsten.<ref name="w-apps">{{cite web|url=http://www.azom.com/details.asp?ArticleID=1264|title=Tungsten Applications - Steel|date=2000-2008|publisher=|accessdate=2008-06-18}}</ref> ]s containing tungsten, like ] and ], are used in ] blades and wear resistant parts and coatings. Applications requiring its high density include ]s, weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in high level race cars in series, such as ] and ]. It is an ideal material to use as a bucking bar for ], where the mass necessary for good results can be achieved in a small, easy to wield bar. In armaments, tungsten, usually alloyed with ] and ] or ] to form heavy alloys, is used in ]s as an alternative to ] but may also be used in cannon shells, ]s and ]s to create supersonic shrapnel. High-density alloys of tungsten may be used in ] (to allow for a smaller diameter and thus tighter groupings) or for ]s (tungsten bead heads allow the fly to sink rapidly). Some types of ] for musical instruments are wound with tungsten wires. Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to ] or ].<ref name="albert"/> Its hardness makes it ideal for ] that will resist scratching, and are ] and will not need polishing, which is especially useful in designs with a brushed finish.<ref name="popsci">{{cite news|url=http://www.popsci.com/diy/article/2008-03/how-make-convincing-fake-gold-bars|title=How to Make Convincing Fake-Gold Bars|last=Gray|first=Theo|date=], ]|publisher=]|accessdate=2008-06-18}}</ref>

Tungsten chemical compounds are used in ]s, inorganic pigments (e.g. ]s), and also as high-temperature ]s (]). ] (WC) is used to make wear-resistant ]s and cutters and knives for drills, ]s, ] and ] tools used by the metalworking, woodworking, ], ] and construction industries.<ref name="daintith"/> Tungsten oxides are used in ] glazes and ]/] tungstates are used widely in ]. Crystal ]s are used as ] in ] and ]. Other salts that contain tungsten are used in the chemical and ] industries.<ref name="desu"/>

Lately, tungsten is used for jewelry because of its longevity and extremely high durability.

==Production==
]
Tungsten is found in the ]s ] (]-] tungstate, FeW]<sub>4</sub>/MnWO<sub>4</sub>), ] (] tungstate, (CaWO<sub>4</sub>), ] and ]. These are mined and used to produce about 37,400 tons of tungsten concentrates per year in 2000.<ref name="production">{{cite news|url=http://minerals.usgs.gov/minerals/pubs/commodity/tungsten/680400.pdf|title=Tungsten|last=Shedd|first=Kim B.|year=2000|publisher=]|accessdate=2008-06-18|format=PDF}}</ref> Over 75% of this production came from ], while most of the remaining production is done in Austria, Bolivia, Portugal, and Russia, while ] produces none.<ref name="production"/>

The extraction of tungsten has several stages, the ore eventually being converted to tungsten (VI) oxide (WO<sub>3</sub>), which is heated with ] or ], producing powdered tungsten.<ref name="SaundersN">{{cite book|last=Saunders|first=Nigel|title=Tungsten and the Elements of Groups 3 to 7 (The Periodic Table)|publisher=Heinemann Library|location=]|month=February | year=2004|isbn=1403435189}}</ref> It can be used in that state or converted into solid bars.

Tungsten can also be extracted by hydrogen reduction of WF<sub>6</sub> (WF<sub>6</sub> + 3H<sub>2</sub> = W + 6HF) or ] (WF<sub>6</sub> + energy = W + 3F<sub>2</sub>).<ref name="manny"/>

==History==
In 1781, ] ascertained that a new ] could be made from scheelite (at the time named tungstenite): ]. Scheele and ] suggested that it could be possible to obtain a new metal by reducing this acid.<ref name="SaundersN"/> In 1783, ] and ] found an acid made from wolframite that was identical to tungstic acid. Later that year, in ], the brothers succeeded in isolating tungsten through reduction of this acid with ]. They are credited with the discovery of the element.<ref name="ITIAnews_0605">{{cite news|url=http://www.itia.info/FileLib/ITIA_Newsletter_June05.pdf|title=ITIA Newsletter|date=June 2005|publisher=International Tungsten Industry Association|accessdate=2008-06-18|format=PDF}}</ref><ref name="ITIAnews_1205">{{cite news|url=http://www.itia.info/FileLib/ITIA_Newsletter_December05.pdf|title=ITIA Newsletter|date=December 2005|publisher=International Tungsten Industry Association|accessdate=2008-06-18|format=PDF}}</ref>

In World War II, tungsten played a significant role in background political dealings. ], 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.<ref name="portugal">{{cite journal|last=Stevens|first=Donald G.|year=1999|title=World War II Economic Warfare: The United States, Britain, and Portuguese Wolfram|journal=The Historian|publisher=|url=http://www.questia.com/googleScholar.qst;jsessionid=LY1PyzmCc1D256Gvh5wpbhxKyTyvcm2FHpMwpcs2wW2XyytCh4pW!956463030?docId=5001286099}}</ref>

==See also==
* ]
* '']'' by ]

==References==
{{reflist|2}}

==Further reading==
* DC/AC Circuits and Electronics: Principles & Applications by Robert K. Herrick, Published by Delmar Learning 2003 for Purdue University

==External links==
{{Commons|Tungsten}}
{{wiktionary|tungsten}}
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{{Compact periodic table}}

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Revision as of 19:27, 13 October 2008

dur da dur