NEON

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., H₂ and O₂). 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/cm³.

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

Simple asphyxiant

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.

Raw materials

Preparation Products