Neon

Vapor pressure
10	fluorine ← neon → sodium
	periodic table
General
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)
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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For other uses, see Neon (disambiguation).

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.

Notable characteristics

Neon is part of the noble gas series in the periodic table. It follows helium in group 18 (former group 8A) and is placed after fluorine in period 2. It is the second-lightest noble gas, after helium. It 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

Neon is often used in signs

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

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]

References
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External links

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