266 | The History and Use of Our Earth’s Chemical Elements Properties

266 | The History and Use of Our Earth’s Chemical Elements Properties

Neon is a monatomic atom that is considered relatively inert. It does not even combine

with itself to form a diatomic molecule, as do some other gases (e.g., H 2 and O 2 ). During the 1960s it was discovered that the noble gases are not really inert. Neon and the heavier noble gases (Kr, Xe, and Rn) can form compounds when in an ionized state with some other elements. For example, neon can form a two-atom ionized molecule of NeH + . Neon has also been 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 is 0.0008999 g/cm3.

Characteristics As with the other noble gases, neon is colorless, tasteless, and odorless. It glows bright red

when electricity is passed through it in an enclosed glass tube. It will turn from a gas to a liquid at –245.92°C, and only under great pressure will it become solid. It is noncombustible and lighter than air, but not as light as helium.

Abundance฀and฀Source Neon is the fourth most abundant element in the universe, but it makes up only 18.18

ppm 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 the surface, it escapes into the atmosphere and is soon dissipated. Some neon is found mixed with natural gas and several minerals

Neon is produced as a secondary product of the fractional distillation of liquid nitrogen and oxygen. Air is liquefied, and as it warms, nitrogen and oxygen boil off, leaving behind several other colder gases, including about 75% neon, which is then passed through activated charcoal to remove hydrogen and other gases.

History Sir William Ramsay (1852–1916) and Morris W. Travers (1872–1961), the discoverers of

krypton, experimented with liquid air, leading them to determine that there were other inert gases in the cold residues of the liquid air after oxygen and nitrogen were collected. They improved their equipment, allowing the gases to be collected separately as they boil off at their own temperatures. They then, in 1898, identified neon as one of these residue gases using a spectrometer, an instrument that identifies each element by its unique lines in the spectrum of light as it is excited, heated, or burned.

Common฀Uses The most common use of neon is in the manufacture of luminescent electric tubes and

specialty high-voltage indicators. Neon is placed in enclosed glass tubes of various shapes with an electrode at each end. When neon gas is ionized by the passing of a high-voltage, low-amps electrical current through it, a bright red color is produced. Other noble gases produce differ- ent colors, and they can be mixed. Unlike incandescent lamps, neon tubes can be bent and formed into unique shapes, including forming words and images for commercial advertising and signage.

267 Examples฀of฀Compounds

Guide to the Elements |

Neon is basically inert and does not normally form compounds. However, it was recently discovered that, under certain conditions of ionization, it could form the ionized two-atom NeH + . Neon is still considered a “noble gas” that is nonreactive.

Hazards Neon is nontoxic. As an asphyxiate gas, it can smother by removing oxygen from the

lungs. ARGON SYMBOL:฀Ar฀ PERIOD:฀3฀ GROUP:฀18฀(VIIIA)฀ ATOMIC฀NO:฀18

ATOMIC฀MASS:฀39.948฀amu฀ VALENCE:฀0฀฀OXIDATION฀STATE:฀0฀ NATURAL฀STATE:฀Gas ORIGIN฀OF฀NAME:฀The฀name฀“argon”฀is฀derived฀from฀the฀Greek฀word฀argos,฀meaning฀

“inactive.” ISOTOPES:฀There฀are฀a฀total฀of฀24฀isotopes฀of฀argon,฀three฀of฀which฀are฀stable.฀They฀are฀

Ar-36,฀which฀constitutes฀just฀0.3365%฀of฀the฀natural฀amount฀of฀argon;฀Ar-38,฀which฀con- tributes฀just฀0.0632%฀to฀the฀amount฀of฀argon฀on฀Earth;฀and฀Ar-40,฀which,฀by฀far,฀consti- tutes฀the฀most฀argon฀on฀Earth,฀99.6003%฀of฀its฀natural฀abundance.

ELECTRON฀CONFIGURATION ฀ Energy฀Levels/Shells/Electrons฀ Orbitals/Electrons

s2,฀p6

฀ 3-M฀=฀8฀

s2,฀p6

Properties Argon is a colorless, odorless, tasteless, chemically inert noble gas that makes up about

0.93% of the Earth’s atmosphere. It is the third most abundant gas in the atmosphere, mean- ing it is more common than carbon dioxide, helium, methane, and hydrogen.