2007 Schools Wikipedia Selection. Related subjects: Chemical elements
|Name, Symbol, Number||neon, Ne, 10|
|Chemical series||noble gases|
|Group, Period, Block||18, 2, p|
|Atomic mass||20.1797 (6) g/mol|
|Electron configuration||1s2 2s2 2p6|
|Electrons per shell||2, 8|
|Density||(0 °C, 101.325 kPa)
|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−1|
|Heat of vaporization||1.71 kJ·mol−1|
|Heat capacity||(25 °C) 20.786 J·mol−1·K−1|
|Crystal structure||cubic face centered|
|Oxidation states||no data|
| Ionization energies
|1st: 2080.7 kJ·mol−1|
|2nd: 3952.3 kJ·mol−1|
|3rd: 6122 kJ·mol−1|
|Atomic radius (calc.)||38 pm|
|Covalent radius||69 pm|
|Van der Waals radius||154 pm|
|Thermal conductivity||(300 K) 49.1 mW·m−1·K−1|
|Speed of sound||(gas, 0 °C) 435 m/s|
|CAS registry number||7440-01-9|
Neon ( IPA: /ˈniːɒn/) 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.
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.
The reddish-orange colour that neon emits in neon lights is widely used to make advertising signs and is also used in long tubular strips in car modification. 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.
Neon ( Greek νέος meaning "new") was discovered by Scottish chemist William Ramsay and English chemist Morris Travers in 1898.
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.