Editing Period 5 element (section)

==p-block elements==

===Indium===
{{main|Indium}}
'''Indium''' is a [[chemical element]] with the symbol '''In''' and [[atomic number]] 49. This rare, very soft, malleable and easily [[Fusible alloy|fusible]] [[other metal]] is chemically similar to [[gallium]] and [[thallium]], and shows the intermediate properties between these two. Indium was discovered in 1863 and named for the [[indigo blue]] line in its spectrum that was the first indication of its existence in zinc ores, as a new and unknown element. The metal was first isolated in the following year. Zinc ores continue to be the primary source of indium, where it is found in compound form. Very rarely the element can be found as grains of native (free) metal, but these are not of commercial importance.

Indium's current primary application is to form transparent electrodes from [[indium tin oxide]] in [[liquid crystal display]]s and [[touchscreen]]s, and this use largely determines its global mining production. It is widely used in thin-films to form lubricated layers (during [[World War II]] it was widely used to coat bearings in high-performance [[aircraft]]). It is also used for making particularly low melting point alloys, and is a component in some lead-free solders.

Indium is not known to be used by any organism. In a similar way to aluminium salts, indium(III) ions can be toxic to the kidney when given by injection, but oral indium compounds do not have the chronic toxicity of salts of heavy metals, probably due to poor absorption in basic conditions. Radioactive indium-111 (in very small amounts on a chemical basis) is used in [[nuclear medicine]] tests, as a [[radiotracer]] to follow the movement of labeled proteins and [[indium leukocyte imaging|white blood cells]] in the body.

===Tin===
{{main|Tin}}
'''Tin''' is a [[chemical element]] with the symbol '''Sn''' (for {{langx|la|stannum}}) and [[atomic number]] 50. It is a [[main-group element|main-group metal]] in [[group 14]] of the [[periodic table]]. Tin shows chemical similarity to both neighboring group 14 elements, [[germanium]] and [[lead]] and has two possible [[oxidation state]]s, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable [[isotope]]s in the periodic table. Tin is obtained chiefly from the [[mineral]] [[cassiterite]], where it occurs as [[tin dioxide]], SnO<sub>2</sub>.

This silvery, [[malleable]] [[post-transition metal]] is not easily [[oxidation|oxidized]] in air and is used to coat other metals to prevent [[corrosion]]. The first [[alloy]], used in large scale since 3000 BC, was [[bronze]], an alloy of tin and [[copper]]<!--[Anatoly F. Fomenko in his book "History: Fiction or Science",[Chronology 1, pg.70] asserts that Tin metallurgy is more complex than that of Copper and metallic tin had not been known during the Bronze Age. It is possible that some metal of a higher fusibility was manufactured using Copper with some minerals rich in tin content]-->. After 600 BC pure metallic tin was produced. [[Pewter]], which is an alloy of 85–90% tin with the remainder commonly consisting of copper, [[antimony]] and lead, was used for [[tableware]] from the [[Bronze Age]] until the 20th century. In modern times tin is used in many alloys, most notably tin/lead soft [[solder]]s, typically containing 60% or more of tin. Another large application for tin is corrosion-resistant [[tin plating]] of steel. Because of its low toxicity, tin-plated metal is also used for food packaging, giving the name to [[tin can]]s, which are made mostly of steel.

===Antimony===
{{main|Antimony}}
'''Antimony''' ({{langx|la|stibium}}) is a toxic [[chemical element]] with the symbol '''Sb''' and an [[atomic number]] of 51. A lustrous grey [[metalloid]], it is found in nature mainly as the [[sulfide mineral]] [[stibnite]] (Sb<sub>2</sub>S<sub>3</sub>). Antimony compounds have been known since ancient times and were used for cosmetics, metallic antimony was also known but mostly identified as [[lead]].

For some time China has been the largest producer of antimony and its compounds, with most production coming from the [[Xikuangshan Mine]] in [[Hunan]]. Antimony compounds are prominent additives for chlorine and bromine containing [[fire retardant]]s found in many commercial and domestic products. The largest application for metallic antimony is as alloying material for lead and tin. It improves the properties of the alloys which are used as in [[solder]]s, bullets and [[ball bearing]]s. An emerging application is the use of antimony in [[microelectronics]].

===Tellurium===
{{main|Tellurium}}
'''Tellurium''' is a [[chemical element]] that has the symbol '''Te''' and [[atomic number]] 52. A brittle, mildly toxic, rare, silver-white [[metalloid]] which looks similar to [[tin]], tellurium is chemically related to [[selenium]] and [[sulfur]]. It is occasionally found in native form, as elemental crystals. Tellurium is far more common in the universe than on Earth. Its extreme [[abundance of the chemical elements|rarity]] in the Earth's crust, comparable to that of [[platinum]], is partly due to its high atomic number, but also due to its formation of a volatile [[hydride]] which caused the element to be lost to space as a gas during the hot nebular formation of the planet.

Tellurium was discovered in [[Transylvania]] (today part of [[Romania]]) in 1782 by [[Franz-Joseph Müller von Reichenstein]] in a mineral containing tellurium and [[gold]]. [[Martin Heinrich Klaproth]] named the new element in 1798 after the Latin word for "earth", ''tellus''. Gold telluride minerals (responsible for the name of [[Telluride, Colorado]]) are the most notable natural gold compounds. However, they are not a commercially significant source of tellurium itself, which is normally extracted as by-product of [[copper]] and [[lead]] production.

Tellurium is commercially primarily used in [[alloy]]s, foremost in steel and copper to improve machinability. Applications in [[Photovoltaic module|solar panels]] and as a [[semiconductor]] material also consume a considerable fraction of tellurium production.

===Iodine===
{{main|Iodine}}
'''Iodine''' is a [[chemical element]] with the symbol '''I''' and [[atomic number]] 53. The name is from [[Ancient Greek|Greek]] {{lang|grc|ἰοειδής}} ''ioeidēs'', meaning violet or purple, due to the color of elemental iodine vapor.<ref>Online Etymology Dictionary, s.v. [http://www.etymonline.com/index.php?term=iodine ''iodine'']. Retrieved 2012-02-07.</ref>

Iodine and its compounds are primarily used in [[nutrition]], and industrially in the production of [[acetic acid]] and certain polymers. Iodine's relatively high atomic number, low toxicity, and ease of attachment to organic compounds have made it a part of many [[radiocontrast|X-ray contrast]] materials in modern medicine. Iodine has only one [[stable isotope]]. A number of iodine radioisotopes are also used in medical applications.

Iodine is found on Earth mainly as the highly water-soluble iodide I<sup>−</sup>, which concentrates it in oceans and brine pools. Like the other [[halogen]]s, free iodine occurs mainly as a [[diatomic]] molecule I<sub>2</sub>, and then only momentarily after being oxidized from iodide by an oxidant like free oxygen.  In the universe and on Earth, iodine's high atomic number makes it a relatively [[Abundance of the chemical elements|rare element]]. However, its presence in ocean water has given it a role in biology (see below).

===Xenon===
{{main|Xenon}}

'''Xenon''' is a [[chemical element]] with the [[chemical symbol|symbol]] '''Xe''' and [[atomic number]] 54. A colorless, heavy, odorless [[noble gas]], xenon occurs in the [[Earth's atmosphere]] in trace amounts.<ref>{{cite encyclopedia
 |author=Staff|year=2007
 |url=http://www.infoplease.com/ce6/sci/A0852881.html
 |title=Xenon|encyclopedia=Columbia Electronic Encyclopedia
 |edition=6th|publisher=Columbia University Press
 |access-date=2007-10-23}}</ref> Although generally unreactive, xenon can undergo a few [[chemical reaction]]s such as the formation of [[xenon hexafluoroplatinate]], the first [[noble gas compound]] to be synthesized.<ref name="lanl">{{cite web
 |author1=Husted, Robert |author2=Boorman, Mollie |date=December 15, 2003
 |url=http://periodic.lanl.gov/54.shtml|title=Xenon
 |publisher=Los Alamos National Laboratory, Chemical Division
 |access-date=2007-09-26
}}</ref><ref>{{cite book
 |last=Rabinovich|first=Viktor Abramovich
 |author2=Vasserman, A. A. |author3=Nedostup, V. I. |author4= Veksler, L. S. |title=Thermophysical properties of neon, argon, krypton, and xenon|year=1988|edition=English-language
 |publisher=Hemisphere Publishing Corp.
 |location=Washington, DC|isbn=0-89116-675-0
 |bibcode=1988wdch...10.....R
 }}—National Standard Reference Data Service of the USSR. Volume 10.</ref><ref name="beautiful">{{cite magazine
 |url=http://www.chem.umn.edu/class/2301/barany03f/fun/beautiful1.pdf
 |title=Chemistry at its Most Beautiful
 |access-date=2007-09-13
 |last=Freemantel
 |first=Michael
 |date=August 25, 2003
 |magazine=Chemical & Engineering News
 |url-status=dead
 |archive-url=https://web.archive.org/web/20160106203608/http://www.chem.umn.edu/class/2301/barany03f/fun/beautiful1.pdf
 |archive-date=January 6, 2016
}}</ref>

Naturally occurring xenon consists of [[Isotopes of xenon|nine stable isotopes]]. There are also over 40 unstable isotopes that undergo [[radioactive decay]]. The isotope ratios of xenon are an important tool for studying the early history of the [[Solar System]].<ref name="kaneoka">{{cite journal
 |last=Kaneoka|first=Ichiro|title=Xenon's Inside Story
 |journal=Science|year=1998|volume=280|issue=5365
 |pages=851–852|doi=10.1126/science.280.5365.851b|s2cid=128502357}}</ref> Radioactive [[xenon-135]] is produced from [[iodine-135]] as a result of [[nuclear fission]], and it acts as the most significant [[neutron absorber]] in [[nuclear reactor]]s.<ref name="stacey">{{cite book
 |first=Weston M.|last=Stacey|year=2007
 |title=Nuclear Reactor Physics|page=213
 |url=https://books.google.com/books?id=y1UgcgVSXSkC&pg=PA213|publisher=Wiley-VCH|isbn=978-3-527-40679-1}}</ref>

Xenon is used in [[xenon flash lamp|flash lamps]]<ref name="burke">{{cite web
 |author=Anonymous|title=History
 |url=http://www.millisecond-cine.com/history.html
 |archive-url=https://web.archive.org/web/20060822141910/http://www.millisecond-cine.com/history.html
 |archive-date=2006-08-22
 |publisher=Millisecond Cinematography
 |access-date=2007-11-07
}}</ref> and [[xenon arc lamp|arc lamps]],<ref name="mellor">{{cite book
 |first=David|last=Mellor|year=2000|page=[https://archive.org/details/soundpersonsguid0000mell/page/186 186]
 |title=Sound Person's Guide to Video
 |publisher=Focal Press
 |isbn=0-240-51595-1|url=https://archive.org/details/soundpersonsguid0000mell|url-access=registration}}</ref> and as a [[general anaesthesia|general anesthetic]].<ref name="Sanders">{{cite journal
 |author1=Sanders, Robert D. |author2=Ma, Daqing |author3=Maze, Mervyn |title=Xenon: elemental anaesthesia in clinical practice
 |journal=British Medical Bulletin
 |year=2005|volume=71|issue=1|pages=115–35
 |doi=10.1093/bmb/ldh034
 |pmid=15728132|doi-access=free}}</ref> The first [[excimer laser]] design used a xenon [[Dimer (chemistry)|dimer]] molecule (Xe<sub>2</sub>) as its [[Active laser medium|lasing medium]],<ref name="basov">{{cite journal
 |doi=10.1070/QE1971v001n01ABEH003011
 |last=Basov|first=N. G.
 |author2=Danilychev, V. A. |author3=Popov, Yu. M.
  |title=Stimulated Emission in the Vacuum Ultraviolet Region
 |journal=Soviet Journal of Quantum Electronics
 |year=1971|volume=1|issue=1|pages=18–22|bibcode = 1971QuEle...1...18B }}</ref> and the earliest [[laser]] designs used xenon flash lamps as [[Laser pumping|pumps]].<ref name="toyserkani">{{cite book
 |last=Toyserkani|first=E.|year=2004
 |author2=Khajepour, A. |author3=Corbin, S. |page=48
 |title=Laser Cladding|publisher=CRC Press
 |isbn=0-8493-2172-7|url=https://books.google.com/books?id=zfvbyCHzVqMC&pg=PA48}}</ref> Xenon is also being used to search for hypothetical [[weakly interacting massive particles]]<ref name="ball">{{cite journal
 |last=Ball|first=Philip|date=May 1, 2002
 |url=http://www.nature.com/news/2002/020429/full/news020429-6.html
 |title=Xenon outs WIMPs|journal=Nature
 |doi=10.1038/news020429-6 |access-date=2007-10-08|url-access=subscription}}</ref> and as the [[propellant]] for [[ion thruster]]s in [[spacecraft]].<ref name="saccoccia">{{cite news
 |last=Saccoccia|first=G. |author2=del Amo, J. G. |author3=Estublier, D.
 |title=Ion engine gets SMART-1 to the Moon
 |date=August 31, 2006|publisher=ESA
 |url=http://www.esa.int/SPECIALS/SMART-1/SEMLZ36LARE_0.html|access-date=2007-10-01}}</ref>