|Name, Symbol, Number||Neon, Ne, 10
|Chemical series||noble gas|
|Group, Period, Block||5, 4, d|
|Appearance||colorless, odorless gas|
|Atomic mass||20.183(1) g/mol|
|Electron configuration||[ He ] 2s2 2p6|
|Electrons per shell||2, 8, 11, 2|
|Density (near r.t.)||0.000825 g·cm−3|
|Liquid density at m.p.||5.5 g·cm−3|
|Melting point||24.56 K|
(-248.67 °C, -415.5 °F)
|Boiling point||27.104 K|
(-246.048 °C, -411 °F)
|Heat of fusion||21.5 kJ·mol−1|
|Heat of vaporization||459 kJ·mol−1|
|Heat capacity||(25 °C) 24.89 J·mol−1·K−1|
|Crystal structure||cubic body centered|
|Electronegativity||Unknown (Pauling scale)|
|Ionization energies||1st: 2080.662 kJ/mol|
|2nd: 3952.325 kJ/mol|
|3rd: 6121.99 kJ/mol|
|Atomic radius||1.54 pm|
|Atomic radius (calc.)||171 pm (Bohr radius)|
|Covalent radius||0.62 pm|
|Electrical resistivity||(20 °C) 197 n Ω·m|
|Thermal conductivity||(300 K) 30.7 W·m−1·K−1|
|Thermal expansion||(25 °C) 8.4 µm·m−1·K−1|
|Speed of sound (thin rod)||(20 °C) 4560 m/s|
|Bulk modulus||(β form) 128 GPa|
|CAS registry number||7440-01-9|
Neon appears as a colorless, odorless, noncombustible, and nonreactive gas. The gas is composed of single atoms and is therefore described as "monatomic." Neon is 2/3 as dense as air and is the second-lightest noble gas, after helium. Because of its low density, neon slowly escapes Earth's atmosphere, making it rare on Earth. Neon can act as a simple asphyxiant. Exposure of a container of neon to prolonged heat or fire may cause it to rupture violently and rocket. Of all the rare gases, neon has the most intense discharge at normal voltages and currents. Neon glows reddish-orange in a vacuum discharge tube.
- The largest use of neon is in making the ubiquitous ‘neon signs’ for advertising. In a vacuum discharge tube neon glows a reddish orange colour. Only the red signs actually contain pure neon. Others contain different gases to give different colours.
- Neon is also used to make high-voltage indicators and switching gear, lightning arresters, diving equipment and lasers.
- Liquid neon is an important cryogenic refrigerant. It has over 40 times more refrigerating capacity per unit volume than liquid helium, and more than 3 times that of liquid hydrogen.
- Neon may be used in the clinical setting as a diagnostic tracer gas in a gas analyzer for a lung diffusion test. Other clinical applications of neon, such as a radiotherapy in various cancers, have been studied.
In 1898, William Ramsay and Morris Travers at University College London isolated krypton gas by evaporating liquid argon. They had been expecting to find a lighter gas which would fit a niche above argon in the periodic table of the elements. They then repeated their experiment, this time allowing solid argon to evaporate slowly under reduced pressure and collected the gas that came off first. This time they were successful, and when they put a sample of the new gas into their atomic spectrometer, it startled them by the brilliant red glow that we now associate with neon signs. Ramsay named the new gas neon, basing it on neos, the Greek word for new.
Neon is non-toxic and has no known biological role.
Neon is the 5th most abundant element in the universe; however, it is rare on Earth, making up only 0.0018% of Earth's atmosphere.
Neon remains, along with hydrogen and helium, in the small fraction of air that resists liquefaction upon cooling to −195.8 °C (−320.4 °F, the boiling point of liquid nitrogen). Neon is isolated from this cold, gaseous mixture by bringing it into contact with activated charcoal, which adsorbs the neon and hydrogen; removal of hydrogen is effected by adding enough oxygen to convert it all to water, which, along with any surplus oxygen, condenses upon cooling. Processing 88,000 pounds of liquid air will produce one pound of neon.
Given the extreme inertness of neon, its compounds are hard to find. It does, however, appear to form an unstable hydrate. In addition, research involving specialized techniques (including mass spectrometry) has shown that neon can form various ions, either by itself or in combination with other elements. These ions include Ne+, (NeAr)+, (NeH)+, and (HeNe+).