Editing Tellurium (section)

==Characteristics==

===Physical properties===
Tellurium has two [[allotrope]]s, crystalline and amorphous. When [[crystal]]line, tellurium is silvery-white with a metallic luster. The crystals are [[trigonal crystal system|trigonal]] and [[chiral]] ([[space group]] 152 or 154 depending on the chirality), like the gray form of [[selenium]]. It is a brittle and easily pulverized metalloid. Amorphous tellurium is a black-brown powder prepared by precipitating it from a solution of [[tellurous acid]] or [[telluric acid]] (Te(OH)<sub>6</sub>).<ref name="lan" /> Tellurium is a [[semiconductor]] that shows greater electrical conductivity in certain directions depending on [[atom]]ic alignment; the conductivity increases slightly when exposed to light ([[photoconductivity]]).<ref>{{Cite book|chapter-url = https://books.google.com/books?id=Ty5Ymlg_Mh0C&pg=PA89|pages = 89–91|isbn = 978-0-8493-8912-2|chapter = Tellurium|publisher = CRC Press|title = Semiconductor materials|first = Lev Isaakovich|last = Berger|year = 1997|url = https://archive.org/details/semiconductormat0000berg/page/89}}</ref> When molten, tellurium is corrosive to copper, [[iron]], and [[stainless steel]]. Of the [[chalcogen]]s (oxygen-family elements), tellurium has the highest melting and boiling points, at {{convert|722.66|and|1261|K|°C}}, respectively.<ref>[http://www.ptable.com/#Property/State Periodic Table]. ptable.com</ref>

===Chemical properties===
Crystalline tellurium consists of parallel helical chains of Te atoms, with three atoms per turn. This gray material resists oxidation by air and is not volatile.<ref>[[#Greenwood|Greenwood]], p. 752</ref>

===Isotopes===
{{Main|Isotopes of tellurium}}
Naturally occurring tellurium has eight isotopes. Six of those isotopes, <sup>120</sup>Te, <sup>122</sup>Te, <sup>123</sup>Te, <sup>124</sup>Te, <sup>125</sup>Te, and <sup>126</sup>Te, are stable. The other two, <sup>128</sup>Te and <sup>130</sup>Te, are slightly radioactive,<ref name="NUBASE">{{Cite journal| last1 = Audi| first1 = G.|title = The NUBASE Evaluation of Nuclear and Decay Properties| journal = Nuclear Physics A| volume = 729| issue = 1| pages = 3–128|publisher = Atomic Mass Data Center| date = 2003| doi = 10.1016/j.nuclphysa.2003.11.001| bibcode=2003NuPhA.729....3A| last2 = Bersillon| first2 = O.| last3 = Blachot| first3 = J.| last4 = Wapstra| first4 = A. H.| url = http://hal.in2p3.fr/in2p3-00014184}}</ref><ref name="Tellurium 128">{{Cite web|title = WWW Table of Radioactive Isotopes: Tellurium|publisher = Nuclear Science Division, Lawrence Berkeley National Laboratory|date = 2008|url = http://ie.lbl.gov/toi/nuclide.asp?iZA=520128|access-date = 2010-01-16|archive-url = https://web.archive.org/web/20100205101344/http://ie.lbl.gov/toi/nuclide.asp?iZA=520128|archive-date = 2010-02-05|url-status = dead}}</ref><ref>{{cite journal|arxiv=hep-ex/0211015|doi= 10.1103/PhysRevC.67.014323|title= New limits on naturally occurring electron capture of <sup>123</sup>Te|journal= Physical Review C|volume= 67|issue= 1|pages= 014323|year= 2003|last1= Alessandrello|first1= A.|last2= Arnaboldi|first2= C.|last3= Brofferio|first3= C.|last4= Capelli|first4= S.|last5= Cremonesi|first5= O.|last6= Fiorini|first6= E.|last7= Nucciotti|first7= A.|last8= Pavan|first8= M.|last9= Pessina|first9= G.|last10= Pirro|first10= S.|last11= Previtali|first11= E.|last12= Sisti|first12= M.|last13= Vanzini|first13= M.|last14= Zanotti|first14= L.|last15= Giuliani|first15= A.|last16= Pedretti|first16= M.|last17= Bucci|first17= C.|last18= Pobes|first18= C.|bibcode= 2003PhRvC..67a4323A|s2cid= 119523039}}</ref> with extremely long half-lives, including 2.2&nbsp;×&nbsp;10<sup>24</sup> years for <sup>128</sup>Te. This is the longest known half-life among all [[radionuclide]]s<ref>{{Cite web|title=Noble Gas Research |publisher=Laboratory for Space Sciences, Washington University in St. Louis |date=2008 |url=http://presolar.wustl.edu/work/noblegas.html |access-date=2013-01-10 |url-status=dead |archive-url=https://web.archive.org/web/20110928143717/http://presolar.wustl.edu/work/noblegas.html |archive-date=September 28, 2011 }}</ref> and is about 160 [[Orders of magnitude (numbers)#1012|trillion]] (10<sup>12</sup>) times the [[Age of the universe|age of the known universe]].

A further 31 artificial [[radioisotope]]s of tellurium are known, with [[atomic mass]]es ranging from 104 to 142 and with half-lives of 19 days or less. Also, 17 [[nuclear isomer]]s are known, with half-lives up to 154 days. Except for [[beryllium-8]] and beta-delayed alpha emission branches in some lighter [[nuclide]]s, tellurium (<sup>104</sup>Te to <sup>109</sup>Te) is the second lightest element with isotopes known to undergo alpha decay, [[antimony]] being the lightest.<ref name="NUBASE" />

The atomic mass of tellurium ({{val|127.60|u=g·mol<sup>−1</sup>}}) exceeds that of iodine ({{val|126.90|u=g·mol<sup>−1</sup>}}), the next element in the periodic table.<ref name="Emsley">{{Cite book|chapter-url = https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA426|isbn = 978-0-19-850340-8|pages = [https://archive.org/details/naturesbuildingb0000emsl/page/426 426–429]|publisher = Oxford University Press|date = 2003|title = Nature's building blocks: an A-Z guide to the elements|chapter = Tellurium|first = John|last = Emsley|url = https://archive.org/details/naturesbuildingb0000emsl/page/426}}</ref>

===Occurrence===
{{see also|Telluride mineral}}
[[File:Tellurium-89043.jpg|thumb|left|Native tellurium crystal on [[sylvanite]] ([[Vatukoula]], [[Viti Levu]], [[Fiji]]). Picture width 2 mm.]]

With an abundance in the Earth's [[crust (geology)|crust]] comparable to that of platinum (about 1&nbsp;μg/kg), tellurium is one of the rarest stable solid elements.<ref>{{Cite book|date=2002|url=https://books.google.com/books?id=g1Kb-xizc1wC&pg=PA396|page=396|title=A handbook of industrial ecology|first1 = Robert U.|last1 = Ayres|first2= Leslie|last2 = Ayres|publisher=Edward Elgar Publishing|isbn=1-84064-506-7}}</ref> In comparison, even [[thulium]] – the rarest of the stable [[lanthanide]]s – has crystal abundances of 500&nbsp;μg/kg (see [[Abundance of the chemical elements]]).<ref>{{Cite journal|doi=10.1103/RevModPhys.28.53|title=Abundances of the Elements|date=1956|last1=Suess|first1=Hans|last2=Urey|first2=Harold|journal=Reviews of Modern Physics|volume=28|issue=1|pages=53–74|bibcode=1956RvMP...28...53S}}</ref>

The rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance. Tellurium is more abundant than [[rubidium]] in the cosmos, though rubidium is 10,000 times more abundant in the Earth's crust. The rarity of tellurium on Earth is thought to be caused by conditions during preaccretional sorting in the solar nebula, when the stable form of certain elements, in the absence of [[oxygen]] and [[water]], was controlled by the reductive power of free [[hydrogen]]. Under this scenario, certain elements that form volatile [[hydride]]s, such as tellurium, were severely depleted through the evaporation of these hydrides. Tellurium and selenium are the heavy elements most depleted by this process.<ref name="Chemical" />

Tellurium is sometimes found in its native (i.e., elemental) form, but is more often found as the tellurides of [[gold]] such as [[calaverite]] and [[krennerite]] (two different [[polymorphism (materials science)|polymorph]]s of AuTe<sub>2</sub>), [[petzite]], Ag<sub>3</sub>AuTe<sub>2</sub>, and [[sylvanite]], AgAuTe<sub>4</sub>. The town of [[Telluride, Colorado]], was named in the hope of a strike of gold telluride (which never materialized, though gold metal ore was found). Gold itself is usually found uncombined, but when found as a chemical compound, it is often combined with tellurium.<ref name="CRC"/>

Although tellurium is found with gold more often than in uncombined form, it is found even more often combined as tellurides of more common metals (e.g. [[melonite]], NiTe<sub>2</sub>). Natural [[tellurite]] and [[tellurate]] minerals also occur, formed by the oxidation of tellurides near the Earth's surface. In contrast to selenium, tellurium does not usually replace sulfur in minerals because of the great difference in ion radii. Thus, many common sulfide minerals contain substantial quantities of selenium and only traces of tellurium.<ref>{{Cite book|chapter = Phase Relations in the Selenide Telluride Systems|pages =217–256| isbn = 978-90-5410-723-1|chapter-url =https://books.google.com/books?id=HUWRZecignoC&pg=PA217|publisher = Taylor & Francis|date = 1996|title = Geochemistry, mineralogy and genesis of gold deposits|first = I. Y.|last = Nekrasov}}</ref>

In the gold rush of 1893, miners in [[Kalgoorlie]] discarded a pyritic material as they searched for pure gold, and it was used to fill in potholes and build sidewalks. In 1896, that tailing was discovered to be [[calaverite]], a telluride of gold, and it sparked a second gold rush that included mining the streets.<ref>{{Cite book|title=The Earth: An Intimate History |last=Fortey |first=Richard |author-link=Richard Fortey |date=2004 |publisher=[[Harper Perennial]]<!-- presumably UK but not sure --> |isbn=978-0-00-257011-4 |page=230}}</ref>

In 2023 astronomers detected the creation of tellurium during collision between two neutron stars.<ref>{{Cite news |last=Sample |first=Ian |last2= |first2= |date=25 October 2023 |title=Creation of rare heavy elements witnessed in neutron-star collision |language=en-GB |work=The Guardian |url=https://www.theguardian.com/science/2023/oct/25/creation-of-rare-heavy-elements-witnessed-in-neutron-star-collision |access-date=26 October 2023 |archive-url=https://web.archive.org/web/20231026082650/https://www.theguardian.com/science/2023/oct/25/creation-of-rare-heavy-elements-witnessed-in-neutron-star-collision |archive-date=26 October 2023 |issn=0261-3077}}</ref>