Editing Xenon (section)

== Characteristics ==
[[File:Solid and liquid xenon.jpg|left|thumb|A layer of solid xenon floating on top of liquid xenon inside a high voltage apparatus]]
[[File:Xe nanoparticles in Al.jpg|thumb|left|Liquid (featureless) and crystalline solid Xe nanoparticles produced by implanting Xe<sup>+</sup> ions into aluminium at room temperature]]
Xenon has [[atomic number]] 54; that is, its nucleus contains 54 [[proton]]s. At [[standard temperature and pressure]], pure xenon gas has a density of 5.894&nbsp;kg/m<sup>3</sup>, about 4.5 times the density of the Earth's atmosphere at sea level, 1.217&nbsp;kg/m<sup>3</sup>.<ref>{{cite web
| last        = Williams
| first       = David R.
| date        = April 19, 2007
| url         = http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
| title       = Earth Fact Sheet
| publisher   = NASA
| access-date = October 4, 2007
}}</ref> As a liquid, xenon has a density of up to 3.100&nbsp;g/mL, with the density maximum occurring at the triple point.<ref name="detectors">{{cite book
| first1    = Elena
| last1     = Aprile
| author2   = Bolotnikov, Aleksey E.
| author3   = Doke, Tadayoshi
| title     = Noble Gas Detectors
| publisher = [[Wiley-VCH]]
| date      = 2006
| isbn      = 3-527-60963-6
| url       = https://books.google.com/books?id=tsnHM8x6cHAC&pg=PT1
| pages     = 8–9
}}</ref> Liquid xenon has a high polarizability due to its large atomic volume, and thus is an excellent solvent. It can dissolve hydrocarbons, biological molecules, and even water.<ref>{{Cite journal
| title        = Xenon as a solvent
| journal      = Nature
| date         = September 10, 1981
| pages        = 165–166
| volume       = 293
| issue        = 5828
| doi          = 10.1038/293165a0
| author-link1 = Peter M. Rentzepis
| first1       = P. M.
| last1        = Rentzepis
| first2       = D. C.
| last2        = Douglass
| s2cid        = 4237285
| bibcode      = 1981Natur.293..165R
}}</ref> Under the same conditions, the density of solid xenon, 3.640&nbsp;g/cm<sup>3</sup>, is greater than the average density of [[granite]], 2.75&nbsp;g/cm<sup>3</sup>.<ref name="detectors" /> Under [[pascal (unit)|gigapascals]] of [[pressure]], xenon forms a metallic phase.<ref>{{cite journal
| last1        = Caldwell
| first1       = W. A.
| author2      = Nguyen, J.
| author3      = Pfrommer, B.
| author4      = Louie, S.
| author5      = Jeanloz, R.
| author-link5 = Raymond Jeanloz
| date         = 1997
| title        = Structure, bonding and geochemistry of xenon at high pressures
| journal      = [[Science (journal)|Science]]
| volume       = 277
| issue        = 5328
| pages        = 930–933
| doi          = 10.1126/science.277.5328.930
}}</ref>

Solid xenon changes from [[Face-centered cubic]] (fcc) to [[Close-packing of spheres|hexagonal close packed]] (hcp) crystal phase under pressure and begins to turn metallic at about 140&nbsp;GPa, with no noticeable volume change in the hcp phase.<ref name=":0">
{{cite web|first=E.|last=Fontes
 |title=Golden Anniversary for Founder of High-pressure Program at CHESS|publisher=Cornell University
 |url=http://news.chess.cornell.edu/articles/2006/RuoffAnnv.html|access-date=May 30, 2009
}}</ref> It is completely metallic at 155&nbsp;GPa.<ref>{{cite journal
| author1     = Eremets, Mikhail I.
| author-link = Mikhail Eremets
| author2     = Gregoryanz, Eugene A.
| author3     = Struzhkin, Victor V.
| author4     = Mao, Ho-Kwang
| author5     = Hemley, Russell J.
| author6     = Mulders, Norbert
| author7     = Zimmerman, Neil M.
| year        = 2000
| title       = Electrical Conductivity of Xenon at Megabar Pressures
| journal     = Physical Review Letters
| volume      = 85
| issue       = 13
| pages       = 2797–800
| bibcode     = 2000PhRvL..85.2797E
| doi         = 10.1103/PhysRevLett.85.2797
| pmid        = 10991236
| s2cid       = 19937739
}}</ref> When metallized, xenon appears sky blue because it absorbs red light and transmits other visible frequencies. Such behavior is unusual for a metal and is explained by the relatively small width of the electron bands in that state.<ref name="Fontes">{{cite web
| first       = E.
| last        = Fontes
| title       = Golden Anniversary for Founder of High-pressure Program at CHESS
| publisher   = Cornell University
| url         = http://news.chess.cornell.edu/articles/2006/RuoffAnnv.html
| access-date = May 30, 2009
}}</ref>{{Better citation needed|reason=The current source is self-published (by a university) and not primarily scientific|date=May 2024}}

[[File:Xenon-flash.gif|thumb|200px|Xenon flashing inside a [[flashtube]] frame by frame]]
Liquid or solid xenon [[nanoparticle]]s can be formed at room temperature by implanting Xe<sup>+</sup> ions into a solid matrix. Many solids have lattice constants smaller than solid Xe. This results in compression of the implanted Xe to pressures that may be sufficient for its liquefaction or solidification.<ref>{{cite journal
| last1   = Iakoubovskii
| first1  = Konstantin
| last2   = Mitsuishi
| first2  = Kazutaka
| last3   = Furuya
| first3  = Kazuo
| title   = Structure and pressure inside Xe nanoparticles embedded in Al
| journal = Physical Review B
| volume  = 78
| issue   = 6
| pages   = 064105
| year    = 2008
| doi     = 10.1103/PhysRevB.78.064105
| s2cid   = 29156048
| bibcode = 2008PhRvB..78f4105I
| url     = https://mdr.nims.go.jp/pid/0e7dcc69-b57a-41e3-8c29-470317925117
}}</ref>

Xenon is a member of the zero-[[Valence (chemistry)|valence]] elements that are called [[noble gas|noble]] or [[inert gas]]es. It is inert to most common chemical reactions (such as combustion, for example) because the outer [[valence shell]] contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound.<ref>{{cite web
| last        = Bader
| first       = Richard F. W.
| url         = http://miranda.chemistry.mcmaster.ca/esam/
| title       = An Introduction to the Electronic Structure of Atoms and Molecules
| publisher   = [[McMaster University]]
| access-date = September 27, 2007
}}</ref>

In a [[gas-filled tube]], xenon emits a [[blue]] or [[lavender (color)|lavenderish]] glow when excited by [[Electric arc|electrical discharge]]. Xenon emits a band of [[Spectral line|emission lines]] that span the visual spectrum,<ref>{{cite web
| last         = Talbot
| first        = John
| url          = http://web.physik.rwth-aachen.de/~harm/aixphysik/atom/discharge/index1.html
| title        = Spectra of Gas Discharges
| publisher    = Rheinisch-Westfälische Technische Hochschule Aachen
| access-date  = August 10, 2006
| url-status   = dead
| archive-url  = https://web.archive.org/web/20070718115616/http://web.physik.rwth-aachen.de/~harm/aixphysik/atom/discharge/index1.html
| archive-date = July 18, 2007
}}</ref> but the most intense lines occur in the region of blue light, producing the coloration.<ref>{{cite book
| first     = William Marshall
| last      = Watts
| date      = 1904
| title     = An Introduction to the Study of Spectrum Analysis
| url       = https://archive.org/details/anintroductiont00hugggoog
| publisher = [[Longmans, Green, and Co.]]
| location  = London
}}</ref>