Atomic Number:


Melting Point: -189.35 șC
Atomic Symbol: Ar Boiling Point:  -185.85 șC
Atomic Weight: 39.948 amu Density: 1.784 kg/m 3
Atomic Radius:

174 pm

Oxidation States: --
Covalent Radius: 97 pm Electron Configuration: [Ne]3s23p6
van der Waals Radius:

188 pm

State of Matter:  gas (nonmagnetic)


(Gr. argos, inactive) Its presence in air was suspected by Cavendish in 1785, discovered by Lord Raleigh and Sir William Ramsay in 1894.


Argon is two and one half times as soluble in water as nitrogen, having about the same solubility as oxygen. Argon is colorless and odorless, both as a gas and liquid. Argon is considered to be a very inert gas and is not known to form true chemical compounds, as do krypton, xenon, and radon.

The creation of argon hydroflouride (HArF) was reported by researchers at the University of Helsinki in 2000. A highly unstable compound with fluorine has been reported but not yet proven. Although no chemical compounds of argon are presently confirmed, argon can form clathrates with water when atoms of it are trapped in a lattice of the water molecules.


The gas is prepared by fractionation of liquid air because the atmosphere contains 0.94% argon. The atmosphere of Mars contains 1.6% of  40Ar and 5 p.p.m. of  36Ar.


It is used in electric light bulbs and in fluorescent tubes at a pressure of about 400 Pa. and in filling photo tubes, glow tubes, etc. Argon is also used as an inert gas shield for arc welding and cutting, as blanket for the production of titanium and other reactive elements, and as a protective atmosphere for growing silicon and germanium crystals. It is also used in technical SCUBA diving to inflate the dry suit, due to its nonreactive, heat isolating effect.

Argon-39 has been used for a number of applications, primarily ice coring. It has also been used for ground water dating.


Naturally occurring argon is a mixture of three isotopes. Twelve other radioactive isotopes are known to exist.


Argon is relatively non-toxic.  The primary health hazard is asphyxiation by displacement of oxygen which may lead to suffocation.  It is necessary to maintain oxygen levels above 19.5%. Contact with the liquid or cold gas can cause freezing of exposed tissue. Argon exposure may cause dizziness, vomiting, excitation, excess salivation, rapid breathing, headaches, drowsiness, stinging of the nose and throat and may result in unconsciousness.