Helium

Helium spectrum

Helium (A_r, standard]]: 4.002602(2)) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.

Characteristics

Helium is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant). It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter.

Discovery and Production

The discovery of helium on Earth was made in the United States in Kansas. Commercial extraction of helium, which is dependent on natural gas extraction, occurs in a small number of places around the world, with the greatest yield in the United States, particularly in Texas, Kansas, and neighboring states.

Uses

Because it is inert and has a low density, helium is used for many purposes that require some of these unique properties. It is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography, because it is inert. Because of its low density, it is used in buoyant applications such as in weather balloons and airships.

Liquefaction

Helium is the most difficult of all gases to liquefy and is impossible to solidify at atmospheric pressure. Its critical temperature, below which it can be liquefied by pressure alone, is the lowest of any known substance. These properties make helium extremely useful in cryogenics.

Health and Safety

Being non-toxic and inert, helium poses no major health hazards and can be handled safely as long as the general precautions for handling gases are followed. However, inhaling helium can be dangerous if done to excess, since it displaces oxygen needed for normal respiration.

See Also

• Periodic Table of Elements
• Inert Gases
• Natural Gas Extraction
• Cryogenics