Difference between revisions of "Neon" - New World Encyclopedia
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− | '''Neon''' | + | '''Neon''' (chemical symbol '''Ne''', [[atomic number]] 10) is a [[chemical element]] that is a colorless, nearly [[inert]] gas under ordinary conditions. It is classified as a [[noble gas]] and is placed in group 18 (former group 8) of the [[periodic table]]. |
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+ | , neon gives a distinct reddish glow when used in vacuum discharge tubes and [[neon lamp]]s and is found in air in trace amounts. | ||
== Notable characteristics == | == Notable characteristics == |
Revision as of 22:01, 16 July 2006
- For other uses, see Neon (disambiguation).
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General | |||||||||||||||||||||||||
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Name, Symbol, Number | neon, Ne, 10 | ||||||||||||||||||||||||
Chemical series | noble gases | ||||||||||||||||||||||||
Group, Period, Block | 18, 2, p | ||||||||||||||||||||||||
Appearance | colorless | ||||||||||||||||||||||||
Atomic mass | 20.1797(6) g/mol | ||||||||||||||||||||||||
Electron configuration | 1s2 2s2 2p6 | ||||||||||||||||||||||||
Electrons per shell | 2, 8 | ||||||||||||||||||||||||
Physical properties | |||||||||||||||||||||||||
Phase | gas | ||||||||||||||||||||||||
Density | (0 °C, 101.325 kPa) 0.9002 g/L | ||||||||||||||||||||||||
Melting point | 24.56 K (-248.59 °C, -415.46 °F) | ||||||||||||||||||||||||
Boiling point | 27.07 K (-246.08 °C, -410.94 °F) | ||||||||||||||||||||||||
Critical point | 44.4 K, 2.76 MPa | ||||||||||||||||||||||||
Heat of fusion | 0.335 kJ/mol | ||||||||||||||||||||||||
Heat of vaporization | 1.71 kJ/mol | ||||||||||||||||||||||||
Heat capacity | (25 °C) 20.786 J/(mol·K) | ||||||||||||||||||||||||
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Atomic properties | |||||||||||||||||||||||||
Crystal structure | cubic face centered | ||||||||||||||||||||||||
Oxidation states | no data | ||||||||||||||||||||||||
Ionization energies (more) |
1st: 2080.7 kJ/mol | ||||||||||||||||||||||||
2nd: 3952.3 kJ/mol | |||||||||||||||||||||||||
3rd: 6122 kJ/mol | |||||||||||||||||||||||||
Atomic radius (calc.) | 38 pm | ||||||||||||||||||||||||
Covalent radius | 69 pm | ||||||||||||||||||||||||
Van der Waals radius | 154 pm | ||||||||||||||||||||||||
Miscellaneous | |||||||||||||||||||||||||
Magnetic ordering | nonmagnetic | ||||||||||||||||||||||||
Thermal conductivity | (300 K) 49.1 mW/(m·K) | ||||||||||||||||||||||||
Speed of sound | (gas, 0 °C) 435 m/s | ||||||||||||||||||||||||
CAS registry number | 7440-01-9 | ||||||||||||||||||||||||
Notable isotopes | |||||||||||||||||||||||||
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Neon (chemical symbol Ne, atomic number 10) is a chemical element that is a colorless, nearly inert gas under ordinary conditions. It is classified as a noble gas and is placed in group 18 (former group 8) of the periodic table.
, 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.[citation needed] 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.[1]
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.[2]
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