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Neon |
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Notable CharacteristicsNeon 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). In most applications it is a less expensive refrigerant[?] than helium. Neon has the most intense discharge at normal voltages and currents of all the rare gases.
ApplicationsThe reddish-orange color that neon emits in neon lights[?] is widely used to make advertising signs. "Neon" is also used generically for these types of lights when in reality many other gases are used to produce different colors of light. Other uses:
Liquefied neon is commercially used as an economical cryogenic refrigerant[?].
HistoryNeon (Greek neos meaning "new") was discovered by William Ramsay and Morris Travers[?] in 1898.
OccurrenceNeon is usually found in the form of a gas with molecules consisting of a single Neon atom. Neon a rare gas that is found in the Earth's atmosphere at 1 part in 65,000 and is produced by supercooling air and fractionally distilling it from the resulting cryogenic liquid.
CompoundsEven though neon is for most practical purposes an inert element, it can form an exotic compound with fluorine in the laboratory. It isn't known for certain if this or any neon compound exists naturally but some evidence suggests that this may be true. The ions, Ne+, (NeAr)+, (NeH)+, and (HeNe+) are have also been observed from optical and mass spectrometric[?] research. In addition, neon forms an unstable hydrate.
IsotopesNeon has three stable isotopes: Ne-20 (90.48%), Ne-21 (0.27%) and Ne-22 (9.25%). Ne-21 and Ne-22 are nucleogenic[?] and their variations are well understood. In contrast, Ne-20 isn't known to be nucleogenic 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 Mg-24 and Mg-25, which produce Ne-21 and Ne-22, 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 Ne-20/Ne-22 and higher Ne-21/Ne-22 ratios observed in uranium-rich rocks such as granites. Isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic production of Ne-21. This isotope is generated by spallation[?] reactions on Mg, Na, Si and Al. 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. Similar to xenon, neon contents observed in samples of volcanic gases are enriched in Ne-20, as well as nucleogenic Ne-21, relative to Ne-22 contents. The neon isotopic contents of these mantle-derived samples represent a non-atmospheric source of neon. The Ne-20-enriched components were attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated Ne-20 abundances were also found in diamonds, further suggesting a solar neon reservoir in the Earth.
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