Neon is a chemical element with symbol Ne and atomic
number 10. It is in group 18 (noble gases) of the periodic table. Neon is a
colorless, odorless, inert monatomic gas under standard conditions, with about
two-thirds the density of air. It was discovered (along with krypton and xenon)
in 1898 as one of the three residual rare inert elements remaining in dry air,
after nitrogen, oxygen, argon and carbon dioxide were removed. Neon was the
second of these three rare gases to be discovered, and was immediately
recognized as a new element from its bright red emission spectrum. The name
neon is derived from the Greek word, νέον, neuter singular form of νέος (neos),
meaning new. Neon is chemically inert and forms no uncharged chemical
compounds. The compounds of neon include ionic molecules, molecules held
together by van der Waals forces and clathrates.
History
Neon (Greek νέον (néon), neuter singular form of νέος
meaning "new"), was discovered in 1898 by the British chemists Sir
William Ramsay (1852–1916) and Morris W. Travers (1872–1961) in London. 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. First 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 "novum", (new), 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." 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.
Applications
Neon is often used in signs and produces an unmistakable
bright reddish-orange light. Although tube lights with other colors are often
called "neon", they use different noble gases or varied colors of
fluorescent lighting.
Neon is used in vacuum tubes, high-voltage indicators,
lightning arresters, 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.
Neon, as liquid or gas, is relatively expensive – for
small quantities, the price of liquid neon can be more than 55 times that of
liquid helium. Driving neon's expense is the rarity of neon, which unlike
helium, can only be obtained from air.
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