Neon

Related Topics:
Neon :: Neonatal :: Neonatal_Circumcision :: Neon_Genesis_Evangelion :: Neonatology :: Neon_and_Cold_Cathode

Neon is the chemical element in the periodic table that has the symbol Ne and atomic number 10. A colorless, nearly inert noble gas, neon gives a distinct reddish glow when used in vacuum discharge tubes and neon lamps and is found in air in trace amounts.

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). 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.

Applications

The reddish-orange color that neon emits in neon lights is widely used to make advertising signs. The word "neon" is also used generically for these types of lights even though many other gases are used to produce different colors of light. Other uses:

vacuum tubes
high-voltage indicators
lightning arrestors
wave meter tubes
television tubes
Neon and helium are used to make a type of gas laser
Liquefied neon is commercially used as a cryogenic refrigerant in applications not requiring the lower temperature range attainable with more expensive liquid helium refrigeration.

History

Neon (Greek νέος meaning "new") was discovered by Scottish chemist William Ramsay and English chemist Morris Travers in 1898.

Occurrence

Neon is a monatomic gas at standard conditions. Neon is rare, found in the Earth's atmosphere at 1 part in 65,000 and industrially produced by cryogenic fractional distillation of liquified air. Neon, like water vapor, is less dense than air; unlike water vapor, which condenses into a liquid below the stratosphere and is thus trapped in Earth's atmosphere, neon may slowly leak out into space, which could explain its scarcity on Earth. Argon, in contrast, is denser than air and so remains within Earth's atmosphere.

Compounds

The ions, Ne⁺, (NeAr)⁺, (NeH)⁺, and (HeNe⁺), have been observed from optical and mass spectrometric research. In addition, neon forms an unstable hydrate.

Isotopes

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 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.^*

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 also found in diamonds, further suggesting a solar neon reservoir in the Earth.^*

References

External links