Neon

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

10 fluorine ← neon → sodium He ↑ Ne ↓ Ar Periodic Table - Extended 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−1
Heat of vaporization	1.71 kJ·mol−1
Heat capacity	(25 °C) 20.786 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 12 13 15 18 21 27
Atomic properties
Crystal structure	cubic face centered
Oxidation states	no data
Ionization energies ( more)	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
Miscellaneous
Magnetic ordering	nonmagnetic
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
Selected isotopes
Main article: Isotopes of neon iso NA half-life DM DE ( MeV) DP 20Ne 90.48% Ne is stable with 10 neutrons 21Ne 0.27% Ne is stable with 11 neutrons 22Ne 9.25% Ne is stable with 12 neutrons
References

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.

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

Neon is often used in signs and produces an unmistakable bright orange colored light. All other colors (though still referred to as "neon") are created using a mercury vapor discharge which excites a phosphor via fluorescence.

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.

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.

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.

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.