This article is about the noble gas. For other uses, see Neon (disambiguation). fluorine ← neon → sodium He ↑ Ne ↓ Ar 10Ne Periodic table Appearance colorless gas exhibiting an orange-red glow when placed in a high voltage electric field Spectral lines of Neon General properties Name, symbol, number neon, Ne, 10 Pronunciation /ˈniːɒn/ Element category noble gases Group, period, block 18, 2, p Standard atomic weight 20.1797g·mol−1 Electron configuration 1s2 2s2 2p6 Electrons per shell 2, 8 (Image) Physical properties Phase gas Density (0 °C, 101.325 kPa) 0.9002 g/L Liquid density at b.p. 1.2071 g·cm−3 Melting point 24.56 K, -248.59 °C, -415.46 °F Boiling point 27.07 K, -246.08 °C, -410.94 °F Triple point 24.5561 K (-249°C), 4323 kPa Critical point 44.4 K, 2.76 MPa Heat of fusion 0.335 kJ·mol−1 Heat of vaporization 1.71 kJ·mol−1 Specific heat capacity (25 °C) 20.786 J·mol−1·K−1 Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 12 13 15 18 21 27 Atomic properties Oxidation states no data Ionization energies (more) 1st: 2080.7 kJ·mol−1 2nd: 3952.3 kJ·mol−1 3rd: 6122 kJ·mol−1 Covalent radius 58 pm Van der Waals radius 154 pm Miscellanea Crystal structure face-centered cubic Magnetic ordering diamagnetic4 Thermal conductivity (300 K) 49.1x10-3  W·m−1·K−1 Speed of sound (gas, 0 °C) 435 m/s Bulk modulus 654 GPa CAS registry number 7440-01-9 Most stable isotopes Main article: Isotopes of neon iso NA half-life DM DE (MeV) DP 20Ne 90.48% 20Ne is stable with 10 neutrons 21Ne 0.27% 21Ne is stable with 11 neutrons 22Ne 9.25% 22Ne is stable with 12 neutrons v · d · e

Neon ( /ˈniːɒn/) is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in discharge tubes and neon lamps and advertising signs.56 It is commercially extracted from air, in which it is found in trace amounts. Contents 1 History 2 Creation 3 Isotopes 4 Characteristics 5 Occurrence 6 Applications 7 Compounds 8 See also 9 References 10 External links // History In the bottom right corner of J. J. Thomson's photographic plate are the separate impact marks for the two isotopes of neon: neon-20 and neon-22. Neon (Greek νέον (neon) meaning "new one") was discovered in 1898 by the British chemists Sir William Ramsay (1852–1916) and Morris W. Travers (1872–1961) in London.7 Neon was discovered when Ramsay chilled a sample of the atmosphere until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases that boiled off, in addition to nitrogen, oxygen, and argon, were krypton, xenon, and neon.8 The characteristic, brilliant red color that is 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."9 Neon's scarcity precluded its prompt application for lighting along the lines of Moore tubes, which used nitrogen and which were commercialized in the early 1900s. After 1902, Georges Claude's company, Air Liquide, was producing industrial quantities of neon as a byproduct of his air liquefaction business, and in December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1912, Claude's associate began selling neon discharge tubes as advertising signs. They were introduced to U.S. in 1923, when two large neon signs were bought by a Los Angeles Packard car dealership. The glow and arresting red colour made neon advertising completely different from the competition.10

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 their deflection by placing a photographic plate in their path. 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 atoms 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 isotopes of stable atoms. It was made by using a crude version of an instrument we now term as a mass spectrometer. Creation Stable forms of neon are produced in stars. It is created in fusing helium and oxygen in the alpha process, which requires temperatures above 100 megakelvin and masses greater than 3 solar masses. Isotopes Main article: Isotopes of neon Neon is the second lightest inert gas. Neon has three stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne (9.25%). 21Ne and 22Ne are nucleogenic and their variations are well understood. In contrast, 20Ne (the cosmogenic primordial isotope made in stellar nucleosynthesis) is not known to be nucleogenic, save for cluster decay production, which is thought to produce only a small amount. The causes of the variation of 20Ne in the Earth have thus been hotly debated.11 The principal nuclear reactions which generate neon isotopes are neutron emission, alpha decay reactions on 24Mg and 25Mg, which produce 21Ne and 22Ne, respectively. The alpha particles are derived from uranium-series decay chains, while the neutrons are mostly produced by secondary reactions from alpha particles. The net result yields a trend towards lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich rocks such as granites. Isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic production of 21Ne. 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 magmatic neon and nucleogenic neon. This suggests that neon will be a useful tool in determining cosmic exposure ages of surficial rocks and meteorites.12

Similar to xenon, neon content observed in samples of volcanic gases are enriched in 20Ne, as well as nucleogenic 21Ne, relative to 22Ne content. The neon isotopic content of these mantle-derived samples represents a non-atmospheric source of neon. The 20Ne-enriched components are attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated 20Ne abundances are found in diamonds, further suggesting a solar neon reservoir in the Earth.13 Characteristics Neon discharge tube Neon is the second-lightest noble gas. It glows reddish-orange in a vacuum discharge tube. Also, neon has the narrowest liquid range of any element: from 24.55 K to 27.05 K (−248.45 °C to −245.95 °C, or −415.21 °F to −410.71 °F). It has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis).1 In most applications it is a less expensive refrigerant than helium.14 Spectrum of neon with ultraviolet (at left) and infrared (at right) lines shown in white Neon plasma has the most intense light discharge at normal voltages and currents of all the noble gases. The average colour 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.15 Two quite different kinds of neon lighting are in common use. Neon glow lamps are typically tiny, and typically operate from 100–250 volts.16 They have been widely used as power-on indicators and in circuit-testing equipment, and were the forerunners of plasma displays and televisions.1718 Neon signs typically operate at larger voltages (2–15 kilovolts), and the luminous tubes can be meters long.19 The glass tubing is typically formed into shapes and letters for signage, architectural, and artistic applications. Occurrence

Neon is actually abundant on a universal scale; it is the fifth most abundant chemical element in the universe by mass, after hydrogen, helium, oxygen, and carbon (see chemical element). 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 which resulted in the formation of 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.20 Mass abundance in the universe is about 1 part in 750 and in the Sun and presumably in the proto-solar system nebula, about 1 part in 600. The Galileo spacecraft atmospheric entry probe found that even 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 even the ice-planetesimals which brought neon into Jupiter from the outer solar system, formed in a region which was too warm for them to have kept their neon (abundances of heavier inert gases on Jupiter are several times that found in the Sun).21 Neon is a monatomic gas at standard conditions. Neon is rare on Earth, found in the Earth's atmosphere at 1 part in 65,000 (by volume) or 1 part in 83,000 by mass. It is industrially produced by cryogenic fractional distillation of liquefied air.1 Applications "Neon" signs may use neon along with other noble gases. Neon gas-discharge lamps forming the symbol for Neon "Ne".

Neon is often used in signs and produces an unmistakable bright reddish-orange light. Although still referred to as "neon", all other colours are generated with the other noble gases or by many colours of fluorescent lighting. Neon is used in vacuum tubes, high-voltage indicators, lightning arrestors, wave meter tubes, television tubes, and helium-neon lasers. Liquefied neon is commercially used as a cryogenic refrigerant in applications not requiring the lower temperature range attainable with more extreme liquid helium refrigeration. Liquid neon is expensive – for small quantities, its price can be more than 55 times that of liquid helium. The driver for expense is rarity of neon, not the liquefaction process. The triple point temperature of neon (24.5561 K) is a defining fixed point in the International Temperature Scale of 1990.2 Compounds Neon is the first p-block noble gas. Neon is generally considered to be inert. No true neutral compounds of neon are known. However, the ions Ne+, (NeAr)+, (NeH)+, and (HeNe+) have been observed from optical and mass spectrometric studies, and there are some unverified reports of an unstable hydrate.1 See also Expansion ratio Neon sign Neon lamp References ^ a b c d Hammond, C.R. (2000). The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. p. 19. ISBN 0849304814. http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf.  ^ a b Preston-Thomas, H. (1990). "The International Temperature Scale of 1990 (ITS-90)". Metrologia 27: 3-10. http://www.bipm.org/en/publications/its-90.html.  ^ "Section 4, Properties of the Elements and Inorganic Compounds; Melting, boiling, triple, and critical temperatures of the elements". CRC Handbook of Chemistry and Physics (85th edition ed.). Boca Raton, Florida: CRC Press. 2005.  ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press. ^ Coyle, Harold P. (2001). Project STAR: The Universe in Your Hands. Kendall Hunt. pp. 464. ISBN 9780787267636. http://books.google.com/?id=KwTzo4GMlewC&pg=PA127.  ^ Kohmoto, Kohtaro (1999). "Phosphors for lamps". In Shionoya, Shigeo; Yen, William M.. Phosphor Handbook. CRC Press. pp. 940. ISBN 9780849375606. http://books.google.com/?id=lWlcJEDukRIC&pg=PA380.  ^ Ramsay, William, Travers, Morris W. (1898). "On the Companions of Argon". Proceedings of the Royal Society of London 63: 437–440. doi:10.1098/rspl.1898.0057.  ^ "Neon: History". Softciências. http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01000.html. Retrieved February 27, 2007.  ^ Weeks, Mary Elvira (2003). Discovery of the Elements: Third Edition (reprint). Kessinger Publishing. p. 287. http://books.google.com/books?id=SJIk9BPdNWcC&pg=PA287.  ^ Mangum, Aja (December 8, 2007). "Neon: A Brief History". New York Magazine. http://nymag.com/shopping/features/41814/.  ^ Dickin, Alan P (2005). "Neon". Radiogenic isotope geology. p. 303. ISBN 9780521823166. http://books.google.com/?id=z8ZCg2HRvWsC&pg=PA303.  ^ "Neon: Isotopes". Softciências. http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01093.html. Retrieved February 27, 2007.  ^ Anderson, Don L.. "Helium, Neon & Argon". Mantleplumes.org. http://www.mantleplumes.org/Ne.html. Retrieved July 2, 2006.  ^ "NASSMC: News Bulletin". December 30, 2005. http://www.nassmc.org/bulletin/dec05bulletin.html#table. Retrieved March 5, 2007.  ^ "Plasma". http://www.electricalfun.com/plasma.htm. Retrieved March 5, 2007.  ^ Baumann, Edward (1966). Applications of Neon Lamps and Gas Discharge Tubes. Carlton Press.  ^ Myers, Robert L. (2002). Display interfaces: fundamentals and standards. John Wiley and Sons. pp. 69–71. ISBN 9780471499466. http://books.google.com/books?id=ilHvFwoAZDMC&pg=PA69. "Plasma displays are closely related to the simple neon lamp."  ^ Weber, Larry F. (April 2006). IEEE Transactions on Plasma Science 34 (2): 268–278. doi:10.1109/TPS.2006.872440.  Paid access. ^ "ANSI Luminous Tube Footage Chart". American National Standards Institute (ANSI). http://www.allanson.com/Product%20PDFs/ANSI_Luminous_footage.pdf. Retrieved 2010-12-10.  Reproduction of a chart in the catalog of a lighting company in Toronto; the original ANSI specification is not given. ^ Gallagher, R.; Ingram, P. (2001-07-19). Chemistry for Higher Tier. University Press. pp. 282. ISBN 9780199148172. http://books.google.com/?id=SJtWSy69eVsC&pg=PA96.  ^ Morse, David (January 26, 1996). "Galileo Probe Science Result". Galileo Project. http://www2.jpl.nasa.gov/sl9/gll38.html. Retrieved February 27, 2007.  External links Wikimedia Commons has media related to: Neon Look up neon in Wiktionary, the free dictionary. The Periodic Table of Videos video of Neon at YouTube WebElements.com – Neon. It's Elemental – Neon USGS Periodic Table – Neon Atomic Spectrum of Neon Neon Museum, Las Vegas v · d · e Periodic table H   He Li Be   B C N O F Ne Na Mg   Al Si P S Cl Ar K Ca   Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr   Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Uuq Uup Uuh Uus Uuo Alkali metals Alkaline earth metals Lanthanides Actinides Transition metals Other metals Metalloids Other nonmetals Halogens Noble gases Large version