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( Neon)
Neon (pronounced /'ni??n/) 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-orange glow when used in discharge tubes and neon lamps.[3][4] It is commercially extracted from air, in which it is found in trace amounts. Neon (Greek ????(neon) meaning "new one") was discovered in 1898 by Scottish chemist William Ramsay (1852 - 1916) and English chemist Morris W. Travers (1872-1961) in London, England.[5] 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 that boiled off were krypton, xenon, and neon.[6] On December 1910, French engineer Georges Claude made a lamp from an electrified tube of neon gas. On January 19, 1915, Claude began selling his tubes to U.S. companies; the Packard car dealership in Los Angeles was one of the first to buy it.[7] 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.[8] 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.[9]
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