Neon

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This article is about the noble gas. For other uses, see Neon (disambiguation).
10 fluorine ← neon → sodium
He
↑
Ne
↓
Ar
General
Name, symbol, number neon, Ne, 10
Chemical series noble gases
Group, period, block 18, 2, p
Appearance colorless
Standard atomic weight 20.1797(6) g·mol−1
Electron configuration 1s2 2s2 2p6
Electrons per shell 2, 8
Physical properties
Color 164
Phase gas
Density (0 °C, 101.325 kPa)
0.9002 g/L
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), 43[1][2] kPa
Critical point 44.4 K, 2.76 MPa
Heat of fusion 0.335 kJ·mol−1
Heat of fusion 98798 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
Crystal structure cubic face centered
Oxidation states no data
Ionization energies
(more)		 1st: 2080.7 kJ·mol−1
2nd: 3952.3 kJ·mol−1
3rd: 6122 kJ·mol−1
Atomic radius (calc.) 38 pm
Covalent radius 69 pm
Van der Waals radius 154 pm
Miscellaneous
Magnetic ordering nonmagnetic
Thermal conductivity (300 K) 49.1x10-3  W·m−1·K−1
Speed of sound (gas, 0 °C) 435 m/s
Bulk modulus 654654 GPa
CAS registry number 7440-01-9
Selected 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
References
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Neon (pronounced /ˈniːɒn/) is the chemical element that has the symbol Ne and atomic number 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 glow when used in vacuum discharge tubes and neon lamps. It is commercially extracted from air, in which it is found in trace amounts.

Contents

[edit] History

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Neon (Greek νέον(neon) meaning "new one") was discovered in 1898 by Scottish chemist William Ramsay (1852 - 1916) and English chemist Morris W. Travers in London, England.[3] 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 three gases were krypton, xenon, and neon.[4] On December 1910, French engineer Georges Claude makes a lamp from an electrified tube of neon glass. On January 19, 1915, Claude begins selling his tubes to U.S. companies; the Packard car dealership in Los Angeles is one of the first to buy.[5]

[edit] Isotopes

Main article: Isotopes of neon

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 is not known to be nucleogenic[citation needed] and the causes of its variation in the Earth have been hotly debated. 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.[6]

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 represent 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.[7]

[edit] Notable characteristics

Neon is the second-lightest noble gas, glows reddish-orange in a vacuum discharge tube and has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis).[8] In most applications it is a less expensive refrigerant than helium.[9] Neon plasma has the most intense light discharge at normal voltages and currents of all the rare gases. The average color of this light to the human eye is red-orange; it contains a strong green line which is hidden, unless the visual components are dispersed by a spectroscope.[10]

[edit] Occurrence

Neon is actually abundant on a universal scale: 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 and chemical inertness, both properties keeping it from being trapped in the condensing gas and dust clouds of the formation of smaller and warmer solid planets like Earth. 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, neon is reduced by about a factor of 10, to 1 part in 6,000 by mass. This may indicate that even the ice-planetesmals 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).[11]

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.[12]

[edit] Applications

Neon is often used in signs and produces an unmistakable bright orange colored light. All other colors (though still referred to as "neon") are created using a mercury vapor discharge which excites a phosphor via fluorescence, or by the other Noble Gases.
Neon is often used in signs and produces an unmistakable bright orange colored light. All other colors (though still referred to as "neon") are created using a mercury vapor discharge which excites a phosphor via fluorescence, or by the other Noble Gases.

The reddish-orange color that neon emits in neon lights is widely used to make advertising signs and is used in long tubular strips in car modification. The word "neon" is used generically for these types of lights even though many other gases are used to produce different colors of light.

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 expensive liquid helium refrigeration.

Neon's triple point temperature of 24.5561 K is a defining fixed point in the International Temperature Scale of 1990.[1]

[edit] Compounds

Neon is a noble gas, and therefore generally considered to be inert. No true compounds of neon are known. However, the ions Ne+, (NeAr)+, (NeH)+, and (HeNe+) have been observed from optical and mass spectrometric studies, and neon is also known to form an unstable hydrate.[13]

[edit] References

  1. ^ a b Preston-Thomas, H. (1990). "The International Temperature Scale of 1990 (ITS-90)". Metrologia 27: 3-10. 
  2. ^ (2005) "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, Boca Raton, Florida: CRC Press. 
  3. ^ William Ramsay, Morris W. Travers (1898). "On the Companions of Argon". Proceedings of the Royal Society of London 63: 437–440. doi:10.1098/rspl.1898.0057. 
  4. ^ Neon: History. Softciências. Retrieved on 2007-02-27.
  5. ^ Neon: A Brief History. New York Magazine. Retrieved on 2008-05-20.
  6. ^ Neon: Isotopes. Softciências. Retrieved on 2007-02-27.
  7. ^ Anderson, Don L.. Helium, Neon & Argon. Mantleplumes.org. Retrieved on 2006-07-02.
  8. ^ Neon (English). Los Almos National Laboratory (15). Retrieved on 2007-03-05.
  9. ^ NASSMC: News Bulletin (English) (30). Retrieved on 2007-03-05.
  10. ^ Plasma. Retrieved on 2007-03-05.
  11. ^ Morse, David (26). Galileo Probe Science Result (English). Galileo Project. Retrieved on 2007-02-27.
  12. ^ Hammond, C. R.. The Elements (English) 19. Fermi National Accelerator Lab. Retrieved on 2007-02-27.
  13. ^ "Periodic Table: Neon." Lawrence Livermore National Laboratory. Last updated on December 15, 2003. Retrieved on August 31, 2007.

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