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The Element Neon

Neon is a 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.

Fluorine Neon
He
Ne
Ar  
 
 
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General
Name, Symbol, Number Neon, Ne, 10
Chemical series Noble gases
Group, Period, Block 18 (VIIIA), 2 , p
Density, Hardness 0.8999 kg/m3 (273 K), NA
Appearance colorless
Atomic properties
Atomic weight 20.1797 amu
Atomic radius (calc.) no data (38) pm
Covalent radius 69 pm
van der Waals radius 154 pm
Electron configuration [He]2s2 2p6
e- 's per energy level 2, 8
Oxidation states (Oxide) 0 (unknown)
Crystal structure Cubic face centered
Physical properties
State of matter gas (nonmagnetic)
Melting point 24.56 K (-415.5 F)
Boiling point 27.07 K (-410.9 F)
Molar volume 13.23 10-6 m3/mol
Heat of vaporization 1.7326 kJ/mol
Heat of fusion 0.3317 kJ/mol
Vapor pressure NA
Speed of sound 435 m/s at 273.15 K
Miscellaneous
Electronegativity no data
Specific heat capacity 103 J/(kg*K)
Electrical conductivity no data
Thermal conductivity 0.0493 W/(m*K)
1st ionization potential 2080.7 kJ/mol
2nd ionization potential 3952.3 kJ/mol
3rd ionization potential 6122 kJ/mol
4th ionization potential 9371 kJ/mol
5th ionization potential 12177 kJ/mol
6th ionization potential 15238 kJ/mol
7th ionization potential 19999.0 kJ/mol
8th ionization potential 23069.5 kJ/mol
SI units & STP are used except where noted.

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. "Neon" is also used generically for these types of lights when in reality many other gases are used to produce different colors of light. Other uses:

  • 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 an economical cryogenic refrigerant.

History

Neon (Greek neos meaning "new") was discovered by William Ramsay and Morris Travers in 1898.

Occurrence

Neon is usually found in the form of a gas with molecules consisting of a single Neon atom. Neon a rare gas that is found in the Earth's atmosphere at 1 part in 65,000 and is produced by supercooling air and fractionally distilling it from the resulting cryogenic liquid.

Compounds

Even though neon is for most practical purposes an inert element, it can form an exotic compound with fluorine in the laboratory. It is not known for certain if this or any neon compound exists naturally but some evidence suggests that this may be true. The ions, Ne+, (NeAr)+, (NeH)+, and (HeNe+) are have also been observed from optical and mass spectrometric research. In addition, neon forms an unstable hydrate.

Isotopes

Neon has three stable isotopes: Ne-20 (90.48%), Ne-21 (0.27%) and Ne-22 (9.25%). Ne-21 and Ne-22 are nucleogenic and their variations are well understood. In contrast, Ne-20 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 Mg-24 and Mg-25, which produce Ne-21 and Ne-22, 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 Ne-20/Ne-22 and higher Ne-21/Ne-22 ratios observed in uranium-rich rocks such as granites. Isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic production of Ne-21. This isotope is generated by spallation reactions on Mg, Na, Si and Al. 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 contents observed in samples of volcanic gases are enriched in Ne-20, as well as nucleogenic Ne-21, relative to Ne-22 contents. The neon isotopic contents of these mantle-derived samples represent a non-atmospheric source of neon. The Ne-20-enriched components were attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated Ne-20 abundances were also found in diamonds, further suggesting a solar neon reservoir in the Earth.

Reference

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