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= Neon =
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Introduction
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Neon is a chemical element; it has symbol Ne and atomic number 10. It
is the second noble gas in the periodic table. Neon is a colorless,
odorless, inert monatomic gas under standard conditions, with
approximately two-thirds the density of air.
Neon was discovered in 1898 alongside krypton and xenon, identified as
one of the three remaining rare inert elements in dry air after the
removal of nitrogen, oxygen, argon, and carbon dioxide. Its discovery
was marked by the distinctive bright red emission spectrum it
exhibited, leading to its immediate recognition as a new element. The
name 'neon' originates from the Greek word , a neuter singular form of
(), meaning 'new'. Neon is a chemically inert gas; although neon
compounds do exist, they are primarily ionic molecules or fragile
molecules held together by van der Waals forces.
The synthesis of most neon in the cosmos resulted from the nuclear
fusion within stars of oxygen and helium through the alpha-capture
process. Despite its abundant presence in the universe and Solar
System--ranking fifth in cosmic abundance following hydrogen, helium,
oxygen, and carbon--neon is comparatively scarce on Earth. It
constitutes about 18.2 ppm of Earth's atmospheric volume and a lesser
fraction in the Earth's crust. The high volatility of neon and its
inability to form compounds that would anchor it to solids explain its
limited presence on Earth and the inner terrestrial planets. Neon’s
high volatility facilitated its escape from planetesimals under the
early Solar System's nascent Sun's warmth.
Neon's notable applications include its use in low-voltage neon glow
lamps, high-voltage discharge tubes, and neon advertising signs, where
it emits a distinct reddish-orange glow. This same red emission line
is responsible for the characteristic red light of helium-neon lasers.
Although neon has some applications in plasma tubes and as a
refrigerant, its commercial uses are relatively limited. It is
primarily obtained through the fractional distillation of liquid air,
making it significantly more expensive than helium due to air being
its sole source.
History
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Neon was discovered in 1898 by the British chemists Sir William Ramsay
(1852-1916) and Morris Travers (1872-1961) in London. Neon was
discovered when Ramsay chilled a sample of air until it became a
liquid, then warmed the liquid and captured the gases as they boiled
off. The gases nitrogen, oxygen, and argon had been identified, but
the remaining gases were isolated in roughly their order of abundance,
in a six-week period beginning at the end of May 1898. The first
remaining gas to be identified was krypton; the next, after krypton
had been removed, was a gas which gave a brilliant red light under
spectroscopic discharge. This gas, identified in June, was named
"neon", the Greek analogue of the Latin ('new') suggested by Ramsay's
son. The characteristic brilliant red-orange color emitted by gaseous
neon when excited electrically was noted immediately. Travers later
wrote: "the blaze of crimson light from the tube told its own story
and was a sight to dwell upon and never forget."
A second gas was also reported along with neon, having approximately
the same density as argon but with a different spectrum - Ramsay and
Travers named it 'metargon'.
However, the subsequent spectroscopic analysis revealed it to be
argon contaminated with carbon monoxide. Finally, the same team
discovered xenon by the same process, in September 1898.
Neon's scarcity precluded its prompt application for lighting along
the lines of Moore tubes, which used nitrogen and which were
commercialized in the early 1900s. After 1902, Georges Claude's
company Air Liquide produced industrial quantities of neon as a
byproduct of his air-liquefaction business. In December 1910 Claude
demonstrated modern neon lighting based on a sealed tube of neon.
Claude tried briefly to sell neon tubes for indoor domestic lighting,
due to their intensity, but the market failed because homeowners
objected to the color. In 1912, Claude's associate began selling neon
discharge tubes as eye-catching advertising signs and was instantly
more successful. Neon tubes were introduced to the U.S. in 1923 with
two large neon signs bought by a Los Angeles Packard car dealership.
The glow and arresting red color made neon advertising completely
different from the competition. The intense color and vibrancy of neon
equated with American society at the time, suggesting a "century of
progress" and transforming cities into sensational new environments
filled with radiating advertisements and "electro-graphic
architecture".
Neon played a role in the basic understanding of the nature of atoms
in 1913, when J. J. Thomson, as part of his exploration into the
composition of canal rays, channeled streams of neon ions through a
magnetic and an electric field and measured the deflection of the
streams with a photographic plate. Thomson observed two separate
patches of light on the photographic plate (see image), which
suggested two different parabolas of deflection. Thomson eventually
concluded that some of the atoms in the neon gas were of higher mass
than the rest. Though not understood at the time by Thomson, this was
the first discovery of isotopes of stable atoms. Thomson's device was
a crude version of the instrument we now term a mass spectrometer.
Isotopes
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Neon has three stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne
(9.25%). 21Ne and 22Ne are partly primordial and partly nucleogenic
(i.e. made by nuclear reactions of other nuclides with neutrons or
other particles in the environment) and their variations in natural
abundance are well understood. In contrast, 20Ne (the chief primordial
isotope made in stellar nucleosynthesis) is not known to be
nucleogenic or radiogenic, except from the decay of oxygen-20, which
is produced in very rare cases of cluster decay by thorium-228. The
causes of the variation of 20Ne in the Earth have thus been hotly
debated.
The principal nuclear reactions generating nucleogenic neon isotopes
start from 24Mg and 25Mg, which produce 21Ne and 22Ne respectively,
after neutron capture and immediate emission of an alpha particle. The
neutrons that produce the reactions are mostly produced by secondary
spallation reactions from alpha particles, in turn derived from
uranium-series decay chains. The net result yields a trend towards
lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich
rocks such as granites.
In addition, isotopic analysis of exposed terrestrial rocks has
demonstrated the cosmogenic (cosmic ray) 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 surface rocks and meteorites.
Neon in solar wind contains a higher proportion of 20Ne than
nucleogenic and cosmogenic sources. Neon content observed in samples
of volcanic gases and diamonds is also enriched in 20Ne, suggesting a
primordial, possibly solar origin.
Characteristics
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Neon is the second-lightest noble gas, after helium. Like other noble
gases, neon is colorless and odorless. It glows reddish-orange in a
vacuum discharge tube. It has over 40 times the refrigerating capacity
(per unit volume) of liquid helium and three times that of liquid
hydrogen. In most applications it is a less expensive refrigerant than
helium. Despite helium surpassing neon in terms of ionization energy,
neon is theorized to be the least reactive of all the elements, even
less so than the former.
Neon plasma has the most intense light discharge at normal voltages
and currents of all the noble gases. The average color of this light
to the human eye is red-orange due to many lines in this range; it
also contains a strong green line, which is hidden, unless the visual
components are dispersed by a spectroscope.
Occurrence
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Stable isotopes of neon are produced in stars. Neon's most abundant
isotope 20Ne (90.48%) is created by the nuclear fusion of carbon and
carbon in the carbon-burning process of stellar nucleosynthesis. This
requires temperatures above 500 megakelvins, which occur in the cores
of stars of more than 8 solar masses.
Neon is abundant on a universal scale; it is the fifth most abundant
chemical element in the universe by mass, after hydrogen, helium,
oxygen, and carbon (see chemical element). Its relative rarity on
Earth, like that of helium, is due to its relative lightness, high
vapor pressure at very low temperatures, and chemical inertness, all
properties which tend to keep it from being trapped in the condensing
gas and dust clouds that formed the smaller and warmer solid planets
like Earth.
Neon is monatomic, making it lighter than the molecules of diatomic
nitrogen and oxygen which form the bulk of Earth's atmosphere; a
balloon filled with neon will rise in air, albeit more slowly than a
helium balloon.
Neon's abundance in the universe is about 1 part in 750 by mass; in
the Sun and presumably in its proto-solar system nebula, about 1 part
in 600. The Galileo spacecraft atmospheric entry probe found that in
the upper atmosphere of Jupiter, the abundance of neon is reduced
(depleted) by about a factor of 10, to a level of 1 part in 6,000 by
mass. This may indicate that the ice-planetesimals that brought neon
into Jupiter from the outer solar system formed in a region that was
too warm to retain the neon atmospheric component (abundances of
heavier inert gases on Jupiter are several times that found in the
Sun), or that neon is selectively sequestered in the planet's
interior.
Neon comprises 1 part in 55,000 in the Earth's atmosphere, or 18.2 ppm
by volume (this is about the same as the molecule or mole fraction),
or 1 part in 79,000 of air by mass. It comprises a smaller fraction in
the crust. It is industrially produced by cryogenic fractional
distillation of liquefied air.
On 17 August 2015, based on studies with the Lunar Atmosphere and Dust
Environment Explorer (LADEE) spacecraft, NASA scientists reported the
detection of neon in the exosphere of the moon.
Chemistry
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Neon is the first p-block noble gas and the first element with a true
octet of electrons. It is inert: as is the case with its lighter
analog, helium, no strongly bound neutral molecules containing neon
have been identified. An example of neon compound is Cr(CO)5Ne, which
contains a very weak Ne-Cr bond. The ions [NeAr]+, [NeH]+, and [HeNe]+
have been observed from optical and mass spectrometric studies. Solid
neon clathrate hydrate was produced from water ice and neon gas at
pressures 350-480 MPa and temperatures about −30 °C. Ne atoms are not
bonded to water and can freely move through this material. They can be
extracted by placing the clathrate into a vacuum chamber for several
days, yielding ice XVI, the least dense crystalline form of water.
The familiar Pauling electronegativity scale relies upon chemical bond
energies, but such values have obviously not been measured for inert
helium and neon. The Allen electronegativity scale, which relies only
upon (measurable) atomic energies, identifies neon as the most
electronegative element, closely followed by fluorine and helium.
The triple point temperature of neon (24.5561 K) is a defining fixed
point in the International Temperature Scale of 1990.
Production
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Neon is produced from air in cryogenic air-separation plants. A
gas-phase mixture mainly of nitrogen, neon, helium, and hydrogen is
withdrawn from the main condenser at the top of the high-pressure
air-separation column and fed to the bottom of a side column for
rectification of the neon. It can then be further purified from helium
by bringing it into contact with activated charcoal. Hydrogen is
purified from the neon by adding oxygen so water is formed and is
condensed. One pound of pure neon can be produced from the processing
of 88,000 pounds of the gas-phase mixture.
Before the 2022 escalation of the war with Russia about 70% of the
global neon supply was produced in Ukraine as a by-product of steel
production in Russia. , the company Iceblick, with plants in Odesa and
Moscow, supplies 65% of the world's production of neon, as well as 15%
of the krypton and xenon.
2022 shortage
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Global neon prices jumped by about 600% after the 2014 Russian
annexation of Crimea, spurring some chip manufacturers to start
shifting away from Russian and Ukrainian suppliers and toward
suppliers in China. The 2022 Russian invasion of Ukraine also shut
down two companies in Ukraine that produced about half of the global
supply: Cryoin Engineering () and Inhaz (), located in Odesa and
Mariupol, respectively. The closure was predicted to exacerbate the
COVID-19 chip shortage, which may further shift neon production to
China.
Lighting and signage
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In neon signs, neon produces an unmistakable bright reddish-orange
light when electric current passes through it under low pressure.
Although tube lights with other colors are often called "neon", they
use different noble gases or varied colors of fluorescent lighting,
for example, argon produces a lavender or blue hue. As of 2012, there
are over one hundred colors available.
Other
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Neon is used in vacuum tubes, high-voltage indicators, lightning
arresters, wavemeter tubes, television tubes, and helium-neon lasers.
Gas mixtures that include high-purity neon are used in lasers for
photolithography in semiconductor device fabrication.
Liquefied neon is commercially used as a cryogenic refrigerant in
applications not requiring the lower temperature range attainable with
the more extreme liquid helium refrigeration.
External links
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* [
http://www.periodicvideos.com/videos/010.htm Neon] at 'The Periodic
Table of Videos' (University of Nottingham)
* [
http://www.webelements.com/neon/ WebElements.com - Neon].
* [
http://education.jlab.org/itselemental/ele010.html It's Elemental -
Neon]
* [
https://wwwrcamnl.wr.usgs.gov/isoig/period/ne_iig.html USGS
Periodic Table - Neon]
* [
http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/atspect2.html
Atomic Spectrum of Neon]
* [
https://www.neonmuseum.org/ Neon Museum, Las Vegas]
License
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License URL:
http://creativecommons.org/licenses/by-sa/3.0/
Original Article:
http://en.wikipedia.org/wiki/Neon
