Neon

Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. 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 no uncharged neon compounds are known. The compounds of neon currently known include ionic molecules, molecules held together by van der Waals forces and clathrates.

History

Neon 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 the atmosphere 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 the Latin novum ('new'), suggested by Ramsay's son. The characteristic brilliant red of the emission spectrum of neon light 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."

Characteristics

At room temperature and pressure, neon diffuses slowly due to its low molecular mass. It is less dense than air and rises in air because of its relative lightness. It also gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or in high-voltage discharge tubes or neon advertising signs. The red emission line from neon also causes the well known red light of helium–neon lasers.

Neon is the second-lightest noble gas, after helium. 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). Most neon is used for neon signs.

Applications

Neon is often used in signs and produces an unmistakable bright reddish-orange light. Although still used in signs, its other uses are now almost entirely confined to lighting, 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.

See also

• Noble gases
• Periodic table
• Chemical element
• Sir William Ramsay
• Morris W. Travers

References

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