The name helium comes from the Greek word helios, meaning sun. French astronomer, Pierre Janssen, discovered helium in the spectrum of the sun during an eclipse in 1868. It was then isolated by Joseph Norman Lockyer using spectral analysis. In 1907, Sir Ernest Rutherford showed that alpha particles are the nuclei of helium atoms. These scientists believed that helium had potential to be a useful element- they were not mistaken.
This monatomic noble gas (group 18) has the symbol He, atomic number two and atomic weight of 4.0026. Helium has a closed electron shell and can absorb energy without being ionized (large ionization potential). Since this inert gas is already stable, it is unlikely to form chemical bonds under normal conditions. Combinations of helium and other elements have been discovered under certain conditions although most compounds are not stable.
Natural gas is the major source of helium. The natural decay of alpha-emitting radioactive minerals in the Earth's crust creates helium, which migrates to areas where gas is trapped. It is extracted from the gas by liquefying and removing all other components of the gas stream. Yet, helium is more abundant in space (stars, nebulae) because it enters the atmosphere and escapes into space due to its low molecular weight.
Helium has many beneficial uses and more are being discovered. There are five distinct properties responsible for its many uses- low density, low boiling point, low solubility, chemical inertness and high thermal conductivity. Since helium is the second lightest and least reactive (non-flammable) element, it is perfect for use in lighter-than-air crafts, weather and research balloons and even toy balloons. Sea divers breathe a helium-oxygen mixture because helium is non-toxic and has a low solubility which overcomes the problem of too much nitrogen dissolving in the blood. In medicine, it is used to relieve sufferers of respiratory difficulties because it promotes oxygen intake and carbon dioxide removal. Small beams of ionized helium atoms have also been used to stabilize or shrink some tumours. Low temperature research (cryogenics) is another application because helium has the lowest melting point of any element and can be cooled almost to absolute zero. Some electrical conductors cooled with liquid helium can even become superconducting (no resistance). Helium is also used to launch rockets and vehicles since it is light and relatively insoluble in fuel and oxidizer fuels and is therefore ideal to fill the tankage as liquids are consumed. It is used as a coolant medium and protective atmosphere in nuclear reactors thanks to its inertness and heat transfer capabilities. Yet another application is in shielded-arc welding because it creates a greater heat release and protects heated parts from attack by air. The last notable use is as a leak detector. It is sensitive and can be used at extreme temperatures.
These many applications and benefits that helium has to offer are just some of the reasons that helium deserves a place in the Chemistry Hall of Fame.
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