Editing Period 6 element (section)

===Tungsten===
{{main|Tungsten}}
'''Tungsten''', also known as '''wolfram''', is a [[chemical element]] with the chemical symbol '''W''' and [[atomic number]] 74. The word ''tungsten'' comes from the Swedish language ''tung sten'' directly translatable to ''heavy stone'',<ref>{{OED|Tungsten}}</ref> though the name is ''volfram'' in Swedish to distinguish it from [[Scheelite]], in Swedish alternatively named ''tungsten''.

A hard, rare [[metal]] under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important [[ore]]s include [[wolframite]] and [[scheelite]]. The [[free element]] is remarkable for its robustness, especially the fact that it has the highest [[melting point]] of all the non-[[alloy]]ed metals and the second highest of all the elements after [[carbon]]. Also remarkable is its high density of 19.3 times that of water, comparable to that of [[uranium]] and [[gold]], and much higher (about 1.7 times) than that of [[lead]].<ref name="daintith">{{cite book |last=Daintith |first=John |title=Facts on File Dictionary of Chemistry |edition=4th |location=New York |publisher=Checkmark Books |year=2005 |isbn=978-0-8160-5649-1 }}</ref> Tungsten with minor amounts of impurities is often [[brittle]]<ref>{{cite book |title=Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds|first = Erik|last = Lassner|author2=Schubert, Wolf-Dieter | publisher = Springer|year = 1999|isbn = 978-0-306-45053-2|chapter-url = https://books.google.com/books?id=foLRISkt9gcC&pg=PA20|chapter = low temperature brittleness|pages = 20–21}}</ref> and [[hardness|hard]], making it difficult to [[metalworking|work]]. However, very pure tungsten, though still hard, is more [[ductility|ductile]], and can be cut with a hard-steel [[hacksaw]].<ref name="albert">{{cite book |last=Stwertka |first=Albert |title=A Guide to the elements |edition=2nd |location=New York |publisher=Oxford University Press |year=2002 |isbn=978-0-19-515026-1 }}</ref>

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent [[light bulb]] filaments, [[X-ray tube]]s (as both the filament and target), electrodes in [[TIG welding]], and [[superalloys]]. Tungsten's hardness and high [[density]] give it military applications in penetrating [[projectile]]s. Tungsten compounds are most often used industrially as [[catalyst]]s.

Tungsten is the only metal from the third [[Transition metal|transition]] series that is known to occur in [[biomolecule]]s, where it is used in a few species of bacteria. It is the heaviest element known to be used by any living organism. Tungsten interferes with [[molybdenum]] and [[copper]]  metabolism, and is somewhat toxic to animal life.<ref>{{cite journal
|title = The active sites of molybdenum- and tungsten-containing enzymes
|author1=McMaster, J.  |author2=Enemark, John H
 |name-list-style=amp |journal = Current Opinion in Chemical Biology
|volume = 2
|issue = 2
|pages = 201–207
|year = 1998
|doi = 10.1016/S1367-5931(98)80061-6
|pmid = 9667924}}</ref><ref>{{cite journal
|title = Molybdenum and tungsten in biology
|author = Hille, Russ
|journal = Trends in Biochemical Sciences
|volume = 27
|issue = 7
|pages = 360–367
|year = 2002
|doi = 10.1016/S0968-0004(02)02107-2
|pmid = 12114025}}</ref>