Difference between revisions of "Neon" - New World Encyclopedia
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'''Neon''' (chemical symbol '''Ne''', [[atomic number]] 10) is a [[chemical element]] that occurs in trace amounts in the air. It is a nearly inert gas and is classified as a [[noble gas]]. Under ordinary conditions, it is colorless, but in a vacuum discharge tube, it gives a reddish-orange glow. | '''Neon''' (chemical symbol '''Ne''', [[atomic number]] 10) is a [[chemical element]] that occurs in trace amounts in the air. It is a nearly inert gas and is classified as a [[noble gas]]. Under ordinary conditions, it is colorless, but in a vacuum discharge tube, it gives a reddish-orange glow. | ||
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+ | == Discovery and occurrence == | ||
+ | |||
+ | Neon (from the [[Greek language|Greek]] word ''νέος'', meaning "new") was discovered in 1898 by Scottish chemist [[William Ramsay]]* and English chemist [[Morris Travers]]*, during their studies of liquefied air. | ||
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+ | Neon is the fourth most abundant element in the [[universe]] [http://education.jlab.org/itselemental/ele010.html]. In the [[Earth's atmosphere]], however, it occurs in only trace amounts—at 1 part in 65,000. It is industrially produced by cryogenic fractional distillation of liquefied air. | ||
== Notable characteristics == | == Notable characteristics == | ||
− | Neon is part of the noble gas series in the [[periodic table]]. As such, it is an unreactive | + | Neon is part of the noble gas series in the [[periodic table]]. As such, it is an extremely unreactive element. The gas is composed of single atoms and is therefore described as "monatomic." |
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+ | Neon follows [[helium]] in group 18 (former group 8A) and is placed after fluorine in period 2. It is less dense than air and is the second-lightest noble gas, after helium. Its low density suggests that it may slowly leak out of the Earth's atmosphere and escape into space, thus providing an explanation for its scarcity on Earth. By contrast, [[argon]] (another noble gas) is denser than air and remains within the Earth's atmosphere. | ||
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+ | Neon has over 40 times the refrigerating capacity of liquid helium and three times that of liquid [[hydrogen]] (on a per unit volume basis). For most applications, it is a less expensive [[refrigerant]]* than helium. | ||
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+ | Of all the rare gases, neon has the most intense discharge at normal voltages and currents. As noted above, it glows reddish-orange in a [[vacuum discharge tube]]*. | ||
== Applications == | == Applications == | ||
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* [[television]] tubes | * [[television]] tubes | ||
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== Compounds == | == Compounds == |
Revision as of 23:57, 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 occurs in trace amounts in the air. It is a nearly inert gas and is classified as a noble gas. Under ordinary conditions, it is colorless, but in a vacuum discharge tube, it gives a reddish-orange glow.
Discovery and occurrence
Neon (from the Greek word νέος, meaning "new") was discovered in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers, during their studies of liquefied air.
Neon is the fourth most abundant element in the universe [1]. In the Earth's atmosphere, however, it occurs in only trace amounts—at 1 part in 65,000. It is industrially produced by cryogenic fractional distillation of liquefied air.
Notable characteristics
Neon is part of the noble gas series in the periodic table. As such, it is an extremely unreactive element. The gas is composed of single atoms and is therefore described as "monatomic."
Neon follows helium in group 18 (former group 8A) and is placed after fluorine in period 2. It is less dense than air and is the second-lightest noble gas, after helium. Its low density suggests that it may slowly leak out of the Earth's atmosphere and escape into space, thus providing an explanation for its scarcity on Earth. By contrast, argon (another noble gas) is denser than air and remains within the Earth's atmosphere.
Neon has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis). For most applications, it is a less expensive refrigerant than helium.
Of all the rare gases, neon has the most intense discharge at normal voltages and currents. As noted above, it glows reddish-orange in a vacuum discharge tube.
Applications
The reddish-orange color that neon emits in neon lamps is widely used for advertising signs. The word "neon" has become a generic term for these types of lights, although many other gases are used to produce different colors of light.
Neon and helium may be used together to make a type of gas laser called a helium-neon laser. In addition, liquefied neon is commercially used as a refrigerant in applications not requiring the lower temperature range attainable with liquid helium, which is more expensive.
Neon is also used in the following devices:
- vacuum tubes
- high-voltage indicators
- lightning arrestors
- wave meter tubes
- television tubes
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.[2]
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.[3]
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