Neon? |
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- This page is about the chemical element. For the automobile, see Dodge Neon. For a new semiconductor technology see ARM. For the fish, see neon tetra. For the light synthesizer, see Neon (light synthesizer).
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| Name, Symbol, Number | neon, Ne, 10 | ||||||||||||||||||||||||
| Chemical series | noble gases | ||||||||||||||||||||||||
| Group, Period, Block | 18, 2, p | ||||||||||||||||||||||||
| Appearance | colorless |
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| 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 |
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| Melting point | 24.56 K (-248.59 °C, -415.46 °F) |
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| Boiling point | 27.07 K (-246.08 °C, -410.94 °F) |
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| 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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| References | |||||||||||||||||||||||||
Neon 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.
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Notable characteristics
Neon is the second-lightest noble gas, glows reddisha href="Orange_03colour04.html" title="Orange (colour)">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. The word "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 Scottish chemist William Ramsay and English chemist Morris Travers in 1898.
Occurrence
Neon is usually found in the form of a gas with molecules consisting of a single neon atom. Neon is 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. Neon, like water vapor, is lighter 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 explains its scarcity on Earth. Argon, in contrast, is heavier than air and so remains within Earth's atmosphere.
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+), 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 uraniumeries 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 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 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.