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{{About|the chemical element}}
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{{Infobox neon}}
'''Neon''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Ne''' and [[atomic number]] 10. It is the second [[noble gas]] in the periodic table.<ref>Group 18 refers to the modern numbering of the periodic table. Older numberings described the rare gases as Group 0 or Group VIIIA (sometimes shortened to 8). See also [[Group (periodic table)]].</ref> Neon is a colorless, odorless, inert [[monatomic gas]] under [[Standard temperature and pressure|standard conditions]], with approximately two-thirds the density of air.

Neon was discovered in 1898 alongside [[krypton]] and [[xenon]], identified as one of the three remaining rare inert elements in dry air after the removal of [[nitrogen]], [[oxygen]], [[argon]], and [[carbon dioxide]]. Its discovery was marked by the distinctive bright red [[emission spectrum]] it exhibited, leading to its immediate recognition as a new element. The name ''neon'' originates from the Greek word {{lang|grc|νέον}}, a neuter singular form of {{lang|grc|νέος}} ({{Transliteration|grc|neos}}), meaning 'new'. Neon is a chemically [[inert gas]]; although [[neon compounds]] do exist, they are primarily ionic molecules or fragile molecules held together by [[van der Waals force]]s.

The synthesis of most neon in the cosmos resulted from the [[Stellar nucleosynthesis|nuclear fusion within stars]] of oxygen and [[helium]] through the [[Alpha process|alpha-capture process]]. Despite its abundant presence in the [[universe]] and [[Solar System]]—ranking fifth in cosmic abundance following hydrogen, helium, oxygen, and carbon—neon is comparatively scarce on Earth. It constitutes about 18.2&nbsp;[[Parts-per notation|ppm]] of Earth's atmospheric volume and a lesser fraction in the Earth's crust. The high [[Volatility (chemistry)|volatility]] of neon and its inability to form compounds that would anchor it to solids explain its limited presence on Earth and the [[Inner planets|inner terrestrial planets]]. Neon's high volatility facilitated its escape from [[planetesimal]]s under the early Solar System's nascent Sun's warmth.

Neon's notable applications include its use in low-[[voltage]] [[neon glow lamp]]s, [[Geissler tube|high-voltage discharge tubes]], and [[Neon sign|neon advertising signs]], where it emits a distinct reddish-orange glow.<ref>{{cite book |title = Project STAR: The Universe in Your Hands|author = Coyle, Harold P. |publisher = Kendall Hunt|date = 2001|isbn = 978-0-7872-6763-6|url = https://books.google.com/books?id=KwTzo4GMlewC&pg=PA127 |page = 464}}</ref><ref>{{cite book|chapter = Phosphors for lamps |title = Phosphor Handbook|editor = Shionoya, Shigeo|editor2 = Yen, William M. |author = Kohmoto, Kohtaro |publisher = CRC Press|date = 1999|isbn = 978-0-8493-7560-6|chapter-url = https://books.google.com/books?id=lWlcJEDukRIC&pg=PA380|page = 940}}</ref> This same red emission line is responsible for the characteristic red light of [[helium–neon laser]]s. Although neon has some applications in plasma tubes and as a refrigerant, its commercial uses are relatively limited. It is primarily obtained through the [[fractional distillation]] of [[liquid air]], making it significantly more expensive than helium due to air being its sole source.

==History==
[[File:NeTube.jpg|thumb|left|Neon [[gas-discharge lamp]]s forming neon's element symbol]]
Neon was discovered in 1898 by the British chemists Sir [[William Ramsay]] (1852–1916) and [[Morris Travers]] (1872–1961) in [[London]].<ref name="RamsayTravers1898"/> Neon was discovered when Ramsay chilled a sample of air until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases [[nitrogen]], [[oxygen]], and [[argon]] had been identified, but the remaining gases were isolated in roughly their order of abundance, in a six-week period beginning at the end of May 1898. The first remaining gas to be identified was [[krypton]]; the next, after krypton had been removed, was a gas which gave a brilliant red light under spectroscopic discharge. This gas, identified in June, was named "neon", the Greek analogue of the Latin {{Lang|la|novum}} ('new')<ref>{{cite web |url=http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01000.html |title=Neon: History |access-date=27 February 2007 |publisher=Softciências |archive-url=https://web.archive.org/web/20070314232318/http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01000.html |archive-date=14 March 2007 }}</ref> suggested by Ramsay's son. The characteristic brilliant red-orange color emitted by gaseous neon when excited electrically was noted immediately. Travers later wrote: "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."<ref>{{cite book|url=https://books.google.com/books?id=SJIk9BPdNWcC&pg=PA287|title=Discovery of the Elements: Third Edition (reprint)|last=Weeks|first=Mary Elvira|date=2003|publisher=Kessinger Publishing|isbn=978-0-7661-3872-8|page=287|author-link=Mary Elvira Weeks|archive-url=https://web.archive.org/web/20150322191804/http://books.google.com/books?id=SJIk9BPdNWcC&pg=PA287|archive-date=22 March 2015|url-status=live}}<!--This is an important quote. It eliminates the many claims that Claude was the first to note the brilliant emission of neon. The probable original source is Travers' 1928 book: {{cite book |title=The Discovery of the Rare Gases |url=https://archive.org/details/discoveryofrareg0000trav |url-access=registration |last=Travers |first=Morris W. |publisher=Edward Arnold & Co. |location=London |year=1928}}--></ref>

A second gas was also reported along with neon, having approximately the same density as argon but with a different spectrum – Ramsay and Travers named it ''metargon''.<ref name="Nobel">
{{cite web
 |url         = https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1904/ramsay-lecture.html
 |title       = Nobel Lecture – The Rare Gases of the Atmosphere
 |last        = Ramsay
 |first       = Sir William
 |date        = 12 December 1904
|website     = nobelprize.org
 |publisher   = Nobel Media AB
 |access-date = 15 November 2015
|url-status     = live
 |archive-url  = https://web.archive.org/web/20151113111406/http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1904/ramsay-lecture.html
 |archive-date = 13 November 2015
}}
</ref><ref name="RamsayTravers1898"/> However, the subsequent spectroscopic analysis revealed it to be argon contaminated with [[carbon monoxide]]. Finally, the same team discovered [[xenon]] by the same process, in September 1898.<ref name="Nobel" />

Neon's scarcity precluded its prompt application for lighting along the lines of [[Moore tube]]s, which used [[nitrogen]] and which were commercialized in the early 1900s. After 1902, [[Georges Claude]]'s company [[Air Liquide]] produced industrial quantities of neon as a byproduct of his air-liquefaction business. In December 1910 Claude demonstrated modern [[neon lighting]] based on a sealed tube of neon. Claude tried briefly to sell neon tubes for indoor domestic lighting, due to their intensity, but the market failed because homeowners objected to the color. In 1912, Claude's associate began selling neon discharge tubes as eye-catching [[neon sign|advertising signs]] and was instantly more successful. Neon tubes were introduced to the U.S. in 1923 with two large neon signs bought by a Los Angeles Packard car dealership. The glow and arresting red color made neon advertising completely different from the competition.<ref>{{cite news
 |url         = http://nymag.com/shopping/features/41814/
 |title       = Neon: A Brief History
 |last        = Mangum
 |first       = Aja
 |access-date = 20 May 2008
 |date        = 8 December 2007
|newspaper   = New York Magazine
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20080415165748/http://nymag.com/shopping/features/41814/
 |archive-date = 15 April 2008
}}</ref> The intense color and vibrancy of neon equated with American society at the time, suggesting a "century of progress" and transforming cities into sensational new environments filled with radiating advertisements and "electro-graphic architecture".<ref>{{Cite journal |last=Golec |first=Michael J. |year=2010 |title=Logo/Local Intensities: Lacan, the Discourse of the Other, and the Solicitation to "Enjoy" |journal=Design and Culture |volume=2 |issue=2|pages=167–181 |doi=10.2752/175470710X12696138525622 |s2cid=144257608 }}</ref><ref>{{Cite news |title=Electro-Graphic Architecture |last=Wolfe |first=Tom |date=October 1968 |work=Architecture Canada }}</ref>

Neon played a role in the basic understanding of the nature of atoms in 1913, when [[J. J. Thomson]], as part of his exploration into the composition of [[canal rays]], channeled streams of neon ions through a magnetic and an electric field and measured the deflection of the streams with a photographic plate. Thomson observed two separate patches of light on the photographic plate (see image), which suggested two different parabolas of deflection. Thomson eventually concluded that some of the [[atom]]s in the neon [[gas]] were of higher mass than the rest. Though not understood at the time by Thomson, this was the first discovery of [[isotope]]s of [[Stable isotope|stable]] atoms. Thomson's device was a crude version of the instrument we now term a [[mass spectrometer]].

==Isotopes==
{{Main|Isotopes of neon}}
[[File:Discovery of neon isotopes.JPG|thumb|left|The first evidence for isotopes of a stable element was provided in 1913 by experiments on neon plasma. In the bottom right corner of [[J. J. Thomson]]'s photographic plate are the separate impact marks for the two isotopes neon-20 and neon-22.]]
Neon has three [[stable isotope]]s: <sup>20</sup>Ne (90.48%), <sup>21</sup>Ne (0.27%) and <sup>22</sup>Ne (9.25%).{{NUBASE2020|ref}} <sup>21</sup>Ne and <sup>22</sup>Ne are partly [[primordial isotope|primordial]] and partly [[nucleogenic]] (i.e. made by nuclear reactions of other nuclides with neutrons or other particles in the environment) and their variations in [[natural abundance]] are well understood. In contrast, <sup>20</sup>Ne (the chief [[primordial isotope]] made in stellar [[nucleosynthesis]]) is not known to be nucleogenic or [[radiogenic]], except from the decay of [[oxygen-20]], which is produced in very rare cases of [[cluster decay]] by [[thorium-228]]. The causes of the variation of <sup>20</sup>Ne in the Earth have thus been hotly debated.<ref>{{cite book|isbn = 978-0-521-82316-6|chapter = Neon|page = 303|title = Radiogenic isotope geology|author1 = Dickin, Alan P|date = 2005| publisher=Cambridge University Press }}</ref><ref name="wwwrcanml"/>

The principal [[nuclear reaction]]s generating nucleogenic neon [[isotope]]s start from <sup>24</sup>Mg and <sup>25</sup>Mg, which produce <sup>21</sup>Ne and <sup>22</sup>Ne respectively, after [[neutron capture]] and immediate emission of an [[alpha particle]]. The [[neutron]]s that produce the reactions are mostly produced by secondary spallation reactions from alpha particles, in turn derived from [[uranium]]-series [[decay chain]]s. The net result yields a trend towards lower <sup>20</sup>Ne/<sup>22</sup>Ne and higher <sup>21</sup>Ne/<sup>22</sup>Ne ratios observed in uranium-rich rocks such as [[granite]]s.<ref name="wwwrcanml">[https://wwwrcamnl.wr.usgs.gov/isoig/period/ne_iig.html Resources on Isotopes Periodic Table—Neon] at the [[U.S. Geological Survey]], by Eric Caldwell, posted January 2004, retrieved 10 February 2011</ref>

In addition, isotopic analysis of exposed terrestrial rocks has demonstrated the [[cosmogenic]] (cosmic ray) production of <sup>21</sup>Ne. This isotope is generated by [[spallation]] reactions on [[magnesium]], [[sodium]], [[silicon]], and [[aluminium]]. By analyzing all three isotopes, the cosmogenic component can be resolved from [[magma]]tic neon and nucleogenic neon. This suggests that neon will be a useful tool in determining cosmic exposure ages of surface rocks and [[meteorite]]s.<ref>{{cite web |url=http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01093.html |title=Neon: Isotopes |access-date=27 February 2007 |publisher=Softciências |archive-url=https://web.archive.org/web/20121115190653/http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01093.html |archive-date=15 November 2012 }}</ref>

Neon in [[solar wind]] contains a higher proportion of <sup>20</sup>Ne than nucleogenic and cosmogenic sources.<ref name="wwwrcanml"/> Neon content observed in samples of [[volcano|volcanic]] [[gas]]es and [[diamond]]s is also enriched in <sup>20</sup>Ne, suggesting a primordial, possibly solar origin.<ref>{{cite web |url=http://www.mantleplumes.org/Ne.html |title=Helium, Neon & Argon |access-date=2 July 2006 |author=Anderson, Don L. |publisher=Mantleplumes.org |url-status=live |archive-url=https://web.archive.org/web/20060528113659/http://www.mantleplumes.org/Ne.html |archive-date=28 May 2006 }}</ref>

==Characteristics==
Neon is the second-lightest noble gas, after [[helium]]. Like other noble gases, neon is colorless and odorless. It glows reddish-orange in a [[discharge tube|vacuum discharge tube]]. It has over 40 times the refrigerating capacity (per unit volume) of liquid helium and three times that of liquid [[hydrogen]].<ref name="CRC" /> In most applications it is a less expensive [[refrigerant]] than helium.<ref>{{cite web |url=http://www.nassmc.org/bulletin/dec05bulletin.html#table |title=NASSMC: News Bulletin |access-date=5 March 2007 |date=30 December 2005 |archive-url=https://web.archive.org/web/20070213072031/http://www.nassmc.org/bulletin/dec05bulletin.html |archive-date=13 February 2007 }}</ref><ref>{{cite book |url=https://books.google.com/books?id=nhVEI52-VE8C&pg=PA195 |page=195|title=Fundamentals of Cryogenic Engineering |isbn=978-81-203-3057-3 |last1=Mukhopadhyay |first1=Mamata |date=2012 |publisher=PHI Learning Pvt. |url-status=live |archive-url=https://web.archive.org/web/20171116145946/https://books.google.com/books?id=nhVEI52-VE8C&pg=PA195 |archive-date=16 November 2017}}</ref> Despite helium surpassing neon in terms of [[ionization energy]], neon is theorized to be the chemically least reactive of all the elements, even less so than the former. Multiple computational studies suggest that helium can form stable chemical species under extreme conditions. The [[Helium hydride ion|helium hydride ion]] HeH⁺ has been experimentally observed, and high-pressure solids such as [[Disodium helide|Na<sub>2</sub>He]] have also been confirmed. Additionally, theoretical works predict that helium hydride fluoride (HHeF), a neutral compound from HeH<sup>+</sup> could be stable under extreme pressure, whereas the analogous neon compound HNeF appears unbound and therefore nonexistent. In contrast, no stable neutral or covalent neon compounds are known to exist under any pressure or temperature.<ref>{{Cite book|url=https://books.google.com/books?id=IoFzgBSSCwEC&pg=PA70|title=Modelling Marvels|last=Lewars|first=Errol G.|publisher=Springer|date=2008|isbn=978-1-4020-6972-7|pages=70–71|bibcode=2008moma.book.....L}}</ref> While a neon-containing anion complex [B<sub>12</sub>(CN)<sub>11</sub>Ne]<sup>-</sup> has been predicted theoretically, its existence has yet to be proven experimentally, leaving neon as the only noble gas for which no compounds have been definitively confirmed to exist.<ref>{{cite journal |last1=Mayer |first1=Martin |last2=Rohdenburg |first2=Markus |last3=van Lessen |first3=Valentin |last4=Nierstenhöfer |first4=Marc C. |last5=Aprà |first5=Edoardo |last6=Grabowsky |first6=Simon |last7=Asmis |first7=Knut R. |last8=Jenne |first8=Carsten |last9=Warneke |first9=Jonas |date=10 March 2020 |title=First steps towards a stable neon compound: observation and bonding analysis of [B<sub>12</sub>(CN)<sub>11</sub>Ne]<sup>-</sup> |url=https://pubs.rsc.org/en/content/articlehtml/2020/cc/d0cc01423k |journal=Royal Society of Chemistry |volume=56 |issue=33 |pages= 4591–4594|doi=10.1039/D0CC01423K |pmid=32207481 |access-date=30 October 2025}}</ref>

[[File:Visible spectrum of neon.jpg|thumb|upright=2.5|center|The [[emission spectrum]] of neon shows individual wavelengths of light contributing to its perceived color when heated.]]
Neon plasma has the most intense light discharge at normal voltages and currents of all the noble gases. The average color of this light to the human eye is red-orange due to many lines in this range; it also contains a strong green line, which is hidden, unless the visual components are dispersed by a spectroscope.<ref>{{cite web |url=http://www.electricalfun.com/plasma.htm |title=Plasma |access-date=5 March 2007 |archive-url=https://web.archive.org/web/20070307005259/http://www.electricalfun.com/plasma.htm |archive-date=7 March 2007 }}</ref>

==Occurrence==
Stable isotopes of neon are produced in stars. Neon's most abundant isotope <sup>20</sup>Ne (90.48%) is created by the [[nuclear fusion]] of [[carbon]] and carbon in the [[carbon-burning process]] of [[stellar nucleosynthesis]]. This requires temperatures above 500 [[megakelvin]]s, which occur in the cores of stars of more than 8 solar masses.<ref>{{Cite book|url=https://books.google.com/books?id=fXcdHyLUVnEC&q=neon+cosmic+nucleosynthesis&pg=PA106|title=Handbook of Isotopes in the Cosmos: Hydrogen to Gallium|last=Clayton|first=Donald|publisher=Cambridge University Press|year=2003|isbn=978-0-521-82381-4|pages=106–107}}</ref><ref>{{cite book|author1=Ryan, Sean G. |author2=Norton, Andrew J. | title=Stellar Evolution and Nucleosynthesis | year=2010 | page=135| isbn=978-0-521-13320-3|publisher=[[Cambridge University Press]]|url=https://books.google.com/books?id=PE4yGiU-JyEC&q=carbong+burning}}</ref>

Neon is abundant on a universal scale; it is the [[Abundance of the chemical elements|fifth most abundant chemical element]] in the universe by mass, after hydrogen, helium, oxygen, and carbon (see [[chemical element]]).<ref>{{cite journal |bibcode=2009ARA&A..47..481A |doi=10.1146/annurev.astro.46.060407.145222 |title=The Chemical Composition of the Sun |journal=Annual Review of Astronomy and Astrophysics |volume=47 |issue=1 |pages=481–522 |year=2009 |last1=Asplund |first1=Martin |last2=Grevesse |first2=Nicolas |last3=Sauval |first3=A. Jacques |last4=Scott |first4=Pat |arxiv=0909.0948|s2cid=17921922 }}</ref> Its relative rarity on Earth, like that of helium, is due to its relative lightness, high vapor pressure at very low temperatures, and chemical inertness, all properties which tend to keep it from being trapped in the condensing gas and dust clouds that formed the smaller and warmer solid planets like Earth. 
Neon is monatomic, making it lighter than the molecules of diatomic nitrogen and oxygen which form the bulk of Earth's atmosphere; a balloon filled with neon will rise in air, albeit more slowly than a helium balloon.<ref>{{cite book |title = Chemistry for Higher Tier |author = Gallagher, R. |author2 = Ingram, P. |publisher = University Press |isbn = 978-0-19-914817-2 |url = https://books.google.com/books?id=SJtWSy69eVsC&pg=PA96 |page = 282 |date = 19 July 2001}}</ref>

Neon's abundance in the universe is about 1 part in 750 by mass; in the Sun and presumably in its proto-solar system nebula, about 1 part in 600.{{citation needed|date=December 2023}} The [[Galileo spacecraft]] atmospheric entry probe found that in the upper atmosphere of Jupiter, the abundance of neon is reduced (depleted) by about a factor of 10, to a level of 1 part in 6,000 by mass. This may indicate that the ice-[[planetesimal]]s that brought neon into Jupiter from the outer solar system formed in a region that was too warm to retain the neon atmospheric component (abundances of heavier inert gases on Jupiter are several times that found in the Sun),<ref>{{cite web |url=http://www2.jpl.nasa.gov/sl9/gll38.html |title=Galileo Probe Science Result |access-date=27 February 2007 |last=Morse |first=David |date=26 January 1996 |publisher=Galileo Project |url-status=live |archive-url=https://web.archive.org/web/20070224232055/http://www2.jpl.nasa.gov/sl9/gll38.html |archive-date=24 February 2007 }}</ref> or that neon is selectively sequestered in the planet's interior.<ref name="Wilson2010">{{citation | title=Sequestration of Noble Gases in Giant Planet Interiors | last1=Wilson | first1=Hugh F. | last2=Militzer | first2=Burkhard | journal=Physical Review Letters | volume=104 | issue=12 | article-number=121101 | id=121101 | date=March 2010 | doi=10.1103/PhysRevLett.104.121101 | pmid=20366523 | bibcode=2010PhRvL.104l1101W | arxiv=1003.5940 | s2cid=9850759 | postscript=. }}</ref>

Neon comprises 1 part in 55,000 in the [[Earth's atmosphere]], or 18.2&nbsp;ppm by volume (this is about the same as the molecule or mole fraction), or 1 part in 79,000 of air by mass. It comprises a smaller fraction in the crust. It is industrially produced by cryogenic [[fractional distillation]] of liquefied air.<ref name="CRC" />

On 17 August 2015, based on studies with the [[Lunar Atmosphere and Dust Environment Explorer]] (LADEE) spacecraft, NASA scientists reported the detection of neon in the [[exosphere]] of the [[moon]].<ref name="NASA-20150817">{{cite web |last=Steigerwald |first=William |title=NASA's LADEE Spacecraft Finds Neon in Lunar Atmosphere |url=http://www.nasa.gov/content/goddard/ladee-lunar-neon |date=17 August 2015 |work=[[NASA]] |access-date=18 August 2015 |url-status=live |archive-url=https://web.archive.org/web/20150819035151/http://www.nasa.gov/content/goddard/ladee-lunar-neon/ |archive-date=19 August 2015 }}</ref>

==Chemistry==
[[File:Ne-water clathrate.png|thumb|Crystal structure of Ne [[clathrate hydrate]]<ref name="hydrate" />|300x300px]]
{{main|Neon compounds}}
Neon is the first [[p-block]] noble gas and the first element with a true octet of electrons. It is [[Chemically inert|inert]]: as is the case with its lighter analog, [[helium]], no strongly bound neutral [[Neon compounds|molecules containing neon]] have been identified. An example of neon compound is Cr(CO)<sub>5</sub>Ne, which contains a very weak Ne-Cr bond.<ref>{{cite journal|last1=Perutz|first1=Robin N.|last2=Turner|first2=James J. |title=Photochemistry of the Group 6 hexacarbonyls in low-temperature matrices. III. Interaction of the pentacarbonyls with noble gases and other matrices|journal=Journal of the American Chemical Society|date=August 1975|volume=97|issue=17|pages=4791–4800 |doi=10.1021/ja00850a001|bibcode=1975JAChS..97.4791P }}</ref> The [[ion]]s [Ne[[argon|Ar]]]<sup>+</sup>, [Ne[[hydrogen|H]]]<sup>+</sup>, and [HeNe]<sup>+</sup> have been observed from optical and [[mass spectrometry|mass spectrometric]] studies.<ref name="CRC" /> Solid neon [[clathrate hydrate]] was produced from water ice and neon gas at pressures 350–480&nbsp;MPa and temperatures about −30&nbsp;°C.<ref>{{cite journal |doi=10.1073/pnas.1410690111 |pmid=25002464 |pmc=4115495 |year=2014 |last1=Yu |first1=X. |title=Crystal structure and encapsulation dynamics of ice II-structured neon hydrate |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=111 |issue=29 |pages=10456–61 |last2=Zhu |first2=J. |last3=Du |first3=S. |last4=Xu |first4=H. |last5=Vogel |first5=S. C. |last6=Han |first6=J. |last7=Germann |first7=T. C. |last8=Zhang |first8=J. |last9=Jin |first9=C. |last10=Francisco |first10=J. S. |last11=Zhao |first11=Y. |bibcode=2014PNAS..11110456Y|doi-access=free }}</ref> Ne atoms are not bonded to water and can freely move through this material. They can be extracted by placing the clathrate into a vacuum chamber for several days, yielding [[ice XVI]], the least dense crystalline form of water.<ref name="hydrate">{{cite journal |doi=10.1038/nature14014 |pmid=25503235 |title=Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate |journal=Nature |volume=516 |issue=7530 |pages=231–3 |year=2014 |last1=Falenty |first1=Andrzej |last2=Hansen |first2=Thomas C. |last3=Kuhs |first3=Werner F. |bibcode=2014Natur.516..231F|s2cid=4464711 }}</ref>

The familiar [[Electronegativity#Pauling electronegativity|Pauling electronegativity scale]] relies upon chemical bond energies, but such values have obviously not been measured for inert helium and neon. The [[Electronegativity#Allen electronegativity|Allen electronegativity scale]], which relies only upon (measurable) atomic energies, identifies neon as the most electronegative element, closely followed by fluorine and helium.<ref>{{cite journal |doi=10.1021/ja00207a003 |title=Electronegativity is the average one-electron energy of the valence-shell electrons in ground-state free atoms|year=1989|author=Allen, Leland C.|journal=Journal of the American Chemical Society |volume=111|pages=9003–9014 |issue=25|bibcode=1989JAChS.111.9003A }}</ref>

The [[triple point]] temperature of neon (24.5561&nbsp;K) is a defining fixed point in the [[International Temperature Scale of 1990]].<ref name="ITS90-1">{{cite web |url=http://www.its-90.com/ |title=The Internet resource for the International Temperature Scale of 1990 |access-date=7 July 2009 |archive-url=https://web.archive.org/web/20090815110916/http://www.its-90.com/ |archive-date=15 August 2009}}</ref>

==Production==
Neon is produced from air in [[cryogenic]] [[air separation|air-separation]] plants. A gas-phase mixture mainly of nitrogen, neon, helium, and hydrogen<ref name="Britannica">{{Cite web |title=Neon {{!}} Definition, Uses, Melting Point, & Facts {{!}} Britannica |url=https://www.britannica.com/science/neon-chemical-element |access-date=2023-06-13 |website=www.britannica.com |language=en}}</ref> is withdrawn from the main condenser at the top of the high-pressure air-separation column and fed to the bottom of a side column for [[Distillation|rectification]] of the neon.<ref>{{cite book|author1=Shreve, R. Norris |author2=Brink, Joseph |title=Chemical Process Industries|date=1977|isbn=0-07-057145-7|page=113|publisher=McGraw-Hill |edition=4th}}</ref> It can then be further purified from helium by bringing it into contact with activated charcoal. Hydrogen is purified from the neon by adding oxygen so water is formed and is condensed.<ref name="Britannica" /> {{convert|1|lbs|kg}} of pure neon can be produced from the processing of {{convert|88000|lbs|kg}} of the gas-phase mixture.<ref name="Britannica" />

Before the [[Russian invasion of Ukraine|2022 escalation of the war with Russia]] about 70% of the global neon supply was produced in [[Ukraine]]<ref>{{cite news |title=Explained: Why the Russia-Ukraine crisis may lead to a shortage in semiconductors|author=Mukul, Pranav | date= 29 March 2022|url=https://www.msn.com/en-in/news/in-depth/explained-why-the-russia-ukraine-crisis-may-lead-to-a-shortage-in-semiconductors/ar-AAUZRlP |work=MSN |publisher=[[The Indian Express]] }}</ref> as a by-product of steel production in [[Russia]].<ref>{{Cite news |last=Alper |first=Alexandra |date=11 March 2022 |title=Exclusive: Russia's attack on Ukraine halts half of world's neon output for chips |work=Reuters |url=https://www.reuters.com/technology/exclusive-ukraine-halts-half-worlds-neon-output-chips-clouding-outlook-2022-03-11/ |access-date=16 March 2022}}</ref> {{As of|2020}}, the company [[Iceblick]], with plants in [[Odesa]] and [[Moscow]], supplies 65% of the world's production of neon, as well as 15% of the [[krypton]] and [[xenon]].<ref name=Newshour>{{cite web |title=Rare Gasses Supplier Known for Innovation |url=https://the-european-times.com/iceblick/ |website=The European Times |date=2020}}</ref><ref name="2022-02-25_Reuters"/>

=== 2022 shortage ===
Global neon prices jumped by about 600% after the [[2014 Russian annexation of Crimea]],<ref name="arstechnica" /> spurring some chip manufacturers to start shifting away from Russian and Ukrainian suppliers<ref name="cnbc">{{cite news |title=Chipmakers see limited impact for now, as Russia invades Ukraine |url=https://www.cnbc.com/2022/02/24/chipmakers-see-limited-impact-russia-invasion-ukraine.html |work=CNBC |date=24 February 2022 }}</ref> and toward suppliers in [[China]].<ref name="2022-02-25_Reuters" /> The [[2022 Russian invasion of Ukraine]] also shut down two companies in Ukraine that produced about half of the global supply: Cryoin Engineering ({{Langx|uk|Кріоін Інжинірінг}}) and Inhaz ({{Langx|uk|ІНГАЗ}}), located in [[Odesa]] and [[Mariupol]], respectively.<ref name="arstechnica">{{cite news |last1=Times |first1=Financial |title=Low on gas: Ukraine invasion chokes supply of neon needed for chipmaking |url=https://arstechnica.com/gadgets/2022/03/low-on-gas-ukraine-invasion-chokes-supply-of-neon-needed-for-chipmaking/ |access-date=13 March 2022 |work=Ars Technica |date=4 March 2022 }}</ref> The closure was predicted to exacerbate the [[2020–present global chip shortage|COVID-19 chip shortage]],<ref name="2022-02-25_Reuters">[https://www.reuters.com/breakingviews/ukraine-war-flashes-neon-warning-lights-chips-2022-02-24/ Ukraine war flashes neon warning lights for chips], [[Reuters]], 25 February 2022</ref><ref name="Newshour" /> which may further shift neon production to China.<ref name="cnbc" />

==Applications==
===Lighting and signage===
{{Main|Neon sign}}
[[File:FLORIST (neon sign).jpg|thumb|Neon sign in a [[Hamden, Connecticut]], florist shop|300x300px]]Two quite different kinds of [[neon lighting]] are in common use. [[Neon lamp|Neon glow lamps]] are generally tiny, with most operating between 100 and 250 [[volts]].<ref name="Baumann">{{cite book |last=Baumann |first=Edward |title=Applications of Neon Lamps and Gas Discharge Tubes |date=1966 |publisher=Carlton Press}}</ref> They have been widely used as power-on indicators and in circuit-testing equipment, but [[light-emitting diodes]] (LEDs) now dominate in those applications. These simple neon devices were the forerunners of [[plasma display|plasma displays and plasma television screens]].<ref name="Myers">{{cite book |last1=Myers |first1=Robert L. |url=https://books.google.com/books?id=ilHvFwoAZDMC&pg=PA69 |title=Display interfaces: fundamentals and standards |date=2002 |publisher=John Wiley and Sons |isbn=978-0-471-49946-6 |pages=69–71 |quote=Plasma displays are closely related to the simple neon lamp. |archive-url=https://web.archive.org/web/20160629141148/https://books.google.com/books?id=ilHvFwoAZDMC&pg=PA69 |archive-date=29 June 2016 |url-status=live}}</ref><ref name="Weber">{{cite journal |last=Weber |first=Larry F. |author-link=Larry F. Weber |date=April 2006 |title=History of the plasma display panel |journal=IEEE Transactions on Plasma Science |volume=34 |issue=2 |pages=268–278 |bibcode=2006ITPS...34..268W |doi=10.1109/TPS.2006.872440 |s2cid=20290119}} Paid access.</ref> [[Neon sign]]s typically operate at much higher voltages (2–15 [[kilovolt]]s), and the luminous tubes are commonly meters long.<ref>{{cite web |title=ANSI Luminous Tube Footage Chart |url=http://www.allanson.com/wp-content/uploads/Product_PDFs/ANSI_Luminous_footage.pdf |url-status=live |archive-url=https://web.archive.org/web/20110206163356/http://www.allanson.com/wp-content/uploads/Product_PDFs/ANSI_Luminous_footage.pdf |archive-date=6 February 2011 |access-date=10 December 2010 |publisher=[[American National Standards Institute]] (ANSI)}} Reproduction of a chart in the catalog of a lighting company in Toronto; the original ANSI specification is not given.</ref> The glass tubing is often formed into shapes and letters for signage, as well as architectural and artistic applications.

In [[neon sign]]s, neon produces an unmistakable bright reddish-orange light when [[electric current]] passes through it under low pressure.<ref>{{Cite web |last=mlblevins |date=2009-06-24 |title=A Brief Summary of the Important Uses of Neon |url=https://sciencestruck.com/uses-of-neon |access-date=2023-08-10 |website=Science Struck |language=en-US}}</ref> Although tube lights with other colors are often called "neon", they use different [[noble gas]]es or varied colors of [[Fluorescent bulb|fluorescent]] lighting, for example, [[argon]] produces a lavender or blue hue.<ref>{{Cite web |last=Nuena |first=Julia |date=2019-09-06 |title=How Do Neon Signs Have Different Colors? |url=https://neonsign.com/how-do-neon-signs-have-different-colors/ |access-date=2023-08-10 |website=NeonSign.com |language=en-US}}</ref> As of 2012, there are over one hundred colors available.<ref name="Thielen">{{cite journal |last=Thielen |first=Marcus |date=August 2005 |title=Happy Birthday Neon! |url=http://www.signmuseum.net/histories/happybirthdayneon.asp |journal=Signs of the Times |archive-url=https://web.archive.org/web/20120303060143/http://www.signmuseum.org/histories/happybirthdayneon.asp |archive-date=2012-03-03}}</ref>

===Other===
Neon is used in [[vacuum tube]]s, high-voltage indicators, [[lightning arrester]]s, [[wavemeter]] tubes, [[television]] tubes, and [[helium–neon laser]]s. Gas mixtures that include high-purity neon are used in lasers for [[photolithography]] in [[semiconductor device fabrication]].<ref name="arstechnica" />

Liquefied neon is commercially used as a [[cryogenic]] [[refrigerant]] in applications not requiring the lower temperature range attainable with the more extreme [[liquid helium]] refrigeration.

{{Subject bar
|book1=Neon
|book2=Period 2 elements
|book3=Noble gases
|book4=Chemical elements (sorted&nbsp;alphabetically)
|book5=Chemical elements (sorted by number)
|portal=Chemistry
|commons=y
|wikt=y
|wikt-search=neon
|v=y
|v-search=Neon atom
|b=y
|b-search=Wikijunior:The Elements/Neon
}}

==References==
{{Reflist|30em}}

==External links==
* [http://www.periodicvideos.com/videos/010.htm Neon] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [http://www.webelements.com/neon/ WebElements.com&nbsp;– Neon].
* [http://education.jlab.org/itselemental/ele010.html It's Elemental&nbsp;– Neon]
* [https://wwwrcamnl.wr.usgs.gov/isoig/period/ne_iig.html USGS Periodic Table&nbsp;– Neon]
* [http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/atspect2.html Atomic Spectrum of Neon]
* [https://www.neonmuseum.org/ Neon Museum, Las Vegas]

{{Noble gases}}
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[[Category:Neon| ]]
[[Category:Chemical elements]]
[[Category:Noble gases]]
[[Category:Coolants]]
[[Category:Refrigerants]]
[[Category:Laser gain media]]
[[Category:Industrial gases]]