The Quiet Gas

Finally we come to the last element in the third Period, Argon (Ar - 18). It has a full 3p electron shell so it is very stable. Argon is a Noble Gas and as such does not significantly react with other elements. It has no known stable compounds at room temperature, nor does it form diatomic molecules with itself. The name Argon comes from the Greek and means "the inactive one". It was the first Noble Gas to be discovered, being isolated from the air in 1894.



Argon is the third most common gas in the atmosphere, being more common than Carbon Dioxide. It is present primarily as the isotope Ar-40 and comes from the decay of radioactive Potassium-40 (K-20) which has a half life of over 1 billion years. Potassium-Argon dating can be used to date very old rocks.

It is used primarily as an inert shielding gas in high temperature industrial processes. It produces a distinctive blue-green light and is used in some fluorescent light applications. Being so readily available in the atmosphere, it is relatively cheap and is used where an inert gas is needed. It has a low thermal conductivity so is also used to reduce heat transfer, as in dual pane windows where it is used to fill the space between the panes.

Argon, being highly inert, is used as a preservative. It is used to replace air in a number of applications such as aerosol cans for varnish and paint, sealed bottles containing high grade chemicals or pharmaceuticals, and wine barrels. Since 2001 it has replaced Helium as the gas used by the National Archives to retard decomposition of such important national documents as the Declaration of Independence and the Constitution. Being a larger atom, it does not leak as quickly as Helium from the sealed display cases.

Argon is also used to humanely euthanize poultry as it can replace the Oxygen in their systems causing suffocation and, being more inert than the reactive Oxygen it replaces, preserve the meat. In high concentrations it stays low to the ground since it is heavier than the other elements in the air allowing the chickens to breathe it in easily. For such an inert element Argon has quite a number of unique uses.