Description
In 1898, Dr William Ramsay and Morris M. Travers, a Scottish
scientist and a British scientist, respectively, discovered neon as
a condensation product in liquefied air, as in a process similar
to that used to collect neon today. Neon’s use in lighting
evolved from discoveries that gases under low pressure conduct
electricity. When some flowing electrons collide with residual
gas in an evacuated glass tube, the resulting ions emit light as
they return to their nonexcited state. The color of the light
depends on the residual gas; neon gas produces a red color and
argon, another inert gas often used in tubes (which are
frequently and incorrectly called neon lights), produces a blue
color. These two basic colors are often modified into many
different hues by the addition of such elements as mercury and
cadmium. The neon found on the Earth is considered to be
primordial in origin. Most of the neon is sequestered in the
Earth’s rocks or dissolved in water, with small amounts
escaping into the atmosphere during geologic weathering. The
escaped gas is slowly lost into space faster than it is replenished.
Consequently, neon constitutes only a small part (0.0018%) of
the Earth’s atmosphere, although this element is estimated to
be the fourth most abundant in the universe.
Chemical Properties
colourless odourless gas
Chemical Properties
Neon is an inert, colorless, odorless, tasteless
gas or liquid.
Physical properties
Neon is a monatomic atom that is considered relatively inert. It does not even combinewith itself to form a diatomic molecule, as do some other gases (e.g., H
2 and O
2). Duringthe 1960s it was discovered that the noble gases are not really inert. Neon and the heaviernoble gases (Kr, Xe, and Rn) can form compounds when in an ionized state with some otherelements. For example, neon can form a two-atom ionized molecule of NeH+. Neon has alsobeen forced to form a compound with fluorine.
Neon’s melting point is –248.59°C, its boiling point is –246.08°C, and its density is0.0008999 g/cm
3.
Isotopes
There are a total of 11 isotopes of neon, three of which are stable. They are Ne-20, which makes up 90.48% of the natural abundance of neon on Earth; Ne-21, whichcontributes just 0.27% to all the neon found in nature; and Ne-22, which contributes9.25% to the natural abundance of neon. All the other isotopes have half-lives rangingfrom 3.746×10
-21 seconds to 3.38 minutes.
Origin of Name
The word “neon” was derived from the Greek word neos, meaning
“new.”
Occurrence
Neon is the fourth most abundant element in the universe, but it makes up only 18.18ppm of the Earth’s atmosphere. It is the 82nd most abundant element on Earth.
Neon is believed to be produced by radioactive decay deep in the Earth. As it rises to thesurface, it escapes into the atmosphere and is soon dissipated. Some neon is found mixed withnatural gas and several minerals.
Neon is produced as a secondary product of the fractional distillation of liquid nitrogenand oxygen. Air is liquefied, and as it warms, nitrogen and oxygen boil off, leaving behindseveral other colder gases, including about 75% neon, which is then passed through activatedcharcoal to remove hydrogen and other gases.
History
Discovered by Ramsay and Travers in 1898. Neon
is a rare gaseous element present in the atmosphere to the extent
of 1 part in 65,000 of air. It is obtained by liquefaction
of air and separated from the other gases by fractional distillation.
Natural neon is a mixture of three isotopes. Fourteen
other unstable isotopes are known. It is very inert element;
however, it is said to form a compound with fluorine. It is still
questionable if true compounds of neon exist, but evidence
is mounting in favor of their existence. The following ions
are known from optical and mass spectrometric studies: Ne+,
(NeAr)+, (NeH)+, and (HeNe+). Neon also forms an unstable
hydrate. In a vacuum discharge tube, neon glows reddish orange.
Of all the rare gases, the discharge of neon is the most
intense at ordinary voltages and currents. Neon is used in
making the common neon advertising signs, which accounts
for its largest use. It is also used to make high-voltage indicators,
lightning arrestors, wave meter tubes, and TV tubes.
Neon and helium are used in making gas lasers. Liquid neon
is now commercially available and is finding important application
as an economical cryogenic refrigerant. It has over 40
times more refrigerating capacity per unit volume than liquid
helium and more than three times that of liquid hydrogen. It is compact, inert, and is less expensive than helium when it
meets refrigeration requirements. Neon costs about $800/80
cu. ft. (2265 l).
Characteristics
As with the other noble gases, neon is colorless, tasteless, and odorless. It glows bright redwhen electricity is passed through it in an enclosed glass tube. It will turn from a gas to a liquidat –245.92°C, and only under great pressure will it become solid. It is noncombustible andlighter than air, but not as light as helium.
Uses
Neon is primarily used in luminous tubes (vacuum electric
discharge tubes), airplane beacons, helium–neon lasers, highvoltage
indicators, cryogenic refrigerant, and laboratory
experiments. Other noble gases, especially helium and xenon,
have been found to be useful in anesthesiology and for
neuroprotection, but the few studies using neon have not
confirmed its usefulness in clinical medicine.
Uses
The most common use of neon is in the manufacture of luminescent electric tubes andspecialty high-voltage indicators. Neon is placed in enclosed glass tubes of various shapes withan electrode at each end. When neon gas is ionized by the passing of a high-voltage, low-ampselectrical current through it, a bright red color is produced. Other noble gases produce differentcolors, and they can be mixed. Unlike incandescent lamps, neon tubes can be bent andformed into unique shapes, including forming words and images for commercial advertisingand signage.
Uses
Gas in neon light tubes; ingredient of gaseous fillers for antifog devices, warning signals, electrical current detectors, high-voltage indicators for high-tension electric lines, lightning arresters, wave-meter tubes; in Ne-He lasers; in mixtures with He and Ar in Geiger counters. Liquid as cryogen to produce low temperetures.
Definition
neon: Symbol Ne. A colourlessgaseous element belonging to group18 (formerly group 0) of the periodictable (the noble gases); a.n. 10;r.a.m. 20.179; d. 0.9 g dm–3; m.p.–248.67°C; b.p. –246.05°C. Neon occursin air (0.0018% by volume) and isobtained by fractional distillation ofliquid air. It is used in dischargetubes and neon lamps, in which ithas a characteristic red glow. It formshardly any compounds (neonfluorides have been reported). The elementwas discovered in 1898 by SirWilliam Ramsey and M. W. Travers.
Definition
An inert colorless odorless
monatomic element of the rare-gas group.
Neon forms no compounds. It occurs in
minute quantities (0.0018% by volume) in
air and is obtained from liquid air. It is
used in neon signs and lights, electrical
equipment, and gas lasers.
Symbol: Ne; m.p. –248.67°C; b.p.
–246.05°C; d. 0.9 kg m–3 (0°C); p.n. 10;
r.a.m. 20.18.
Production Methods
Neon is derived commercially from the atmosphere. It is recovered from air after separation of oxygen and nitrogen in air separation plants. The recovery process is based on liquefaction of air. Neon and helium have boiling points below that of liquid air. Thus, at liquid air temperature, nitrogen, oxygen, argon, krypton, and xenon remain in the liquid form, while a gas stream consisting of neon, helium, and some nitrogen is collected as gaseous mixture. The composition of this mixture can vary with the condenser and rate of withdrawal. Nitrogen is removed further by passing the gaseous mixture at 5 to 6 atm through a condenser maintained at liquid nitrogen temperatures. The residue after this step contains neon as the major component, with significant amounts of helium, hydrogen, and nitrogen.
Such crude neon mixture is purified by various chemical and physical processes. Hydrogen is separated by chemically oxidizing it to water, which is removed by drying. Remaining nitrogen from the crude neon is removed by adsorption over charcoal at the liquid nitrogen temperature. After the removal of nitrogen and hydrogen, the technical grade neon may contain about 75% neon and 25% helium. Such neon-helium mixtures may be further separated into their individual components either by differential absorption on charcoal at cold temperatures or by fractional distillation of their liquefied mixture. Fractional distillation, based on the difference of boiling points between helium (-269°C) and neon (-223°C), is the more expensive process. Neon also may be obtained in liquid form if the charcoal in the adsorption process is maintained at its liquefaction temperature. Process conditions may vary depending on purity of the product desired.
Definition
Inert element of atomic number 10, noble gas group
of the periodic table, aw 20.179. Three stable isotopes
General Description
A colorless odorless noncombustible gas. Chemically inert. The vapors are lighter than air. Nontoxic, but can act as a simple asphyxiant. Exposure of the container to prolonged heat or fire may cause NEON to rupture violently and rocket. Principal use is to fill lamp bulbs and tubes.
Reactivity Profile
These substances undergo no chemical reactions under any known circumstances. They are nonflammable, noncombustible and nontoxic. They can asphyxiate.
Hazard
Neon is nontoxic. As an asphyxiate gas, it can smother by removing oxygen from thelungs.
Health Hazard
Vapors may cause dizziness or asphyxiation without warning. Vapors from liquefied gas are initially heavier than air and spread along ground.
Fire Hazard
Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket.
Safety Profile
An inert asphpant gas.
Potential Exposure
Neon is used in photoelectric bulbs
and certain light tubes; in the electronic industry; in lasers;
in plasma studies; and other research.
Shipping
UN1065 Neon and UN1913 Neon, refrigerated
liquid (cryogenic liquid), Hazard Class: 2.2; Labels:
2.2-Nonflammable compressed gas. Cylinders must be
transported in a secure upright position, in a well-ventilated
truck. Protect cylinder and labels from physical damage.
The owner of the compressed gas cylinder is the only entity
allowed by federal law (49CFR) to transport and refill
them. It is a violation of transportation regulations to refill
compressed gas cylinders without the express written
permission of the owner.
Purification Methods
Pass the gas through a copper coil packed with 60/80 mesh 13X molecular sieves which is cooled in liquid N2, or through a column of Ascarite (NaOH-coated silica adsorbent).
Toxicity evaluation
Neon gas is a simple asphyxiant. It displaces the oxygen
necessary to support life. When normal levels of oxygen are not
present in the body, then all tissues, organs, and organ systems
eventually malfunction. Tissues with particularly high oxygen
and energy requirements, including the brain and heart, are
particularly susceptible to harmful effects resulting from
reduced levels of oxygen in the body.
Incompatibilities
Compressed neon gas under pressure
may explode when heated.
Waste Disposal
Return refillable compressed
gas cylinders to supplier. Venting to atmosphere.
