Argon: the essentials

Argon is a colourless and odourless gas present to a very small extent in the atmosphere. Argon is very inert (indeed it is referred to as one of the noble gases) and is not known to form true chemical compounds. It makes a good atmosphere for working with air-sensitive materials since it is heavier than air and less reactive than N2. Today, the chemical symbol for argon is Ar but until 1957 its sybol was simply A.

Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.

Argon: historical information

Argon was discovered by Sir William Ramsay, Lord Rayleigh in 1894 at UCL, London, England. Origin of name: from the Greek word "argos" meaning "inactive".

Argon was discovered by Lord Rayleigh and Sir William Ramsay in 1894. It was isolated by examination of the residue obtained by removing nitrogen, oxygen, carbon dioxide, and water from clean air. In fact, air contains less than 1% argon. The atmosphere of Mars contains less than 2% argon. It was recognized by the characteristic lines in the red end of the spectrum.

Argon around us Read more »

Argon has no biological role.

Argon is present in the atmosphere which contains nearly 1% argon gas.

Abundances for argon in a number of different environments. More abundance data »
Location ppb by weight ppb by atoms Links
Universe 200000 6000 Chemical elements abundance by weight in the universe on a miniature periodic table spark table
Crustal rocks 1500 780 Chemical elements abundance by weight in the earth's crust on a miniature periodic table spark table
Human (no data) ppb by weight (no data) atoms relative to C = 1000000 Chemical elements abundance by weight in humans on a miniature periodic table spark table

Physical properties Read more »

Heat properties Read more »

Crystal structure Read more »

The solid state structure of argon is: ccp (cubic close-packed).

Argon: orbital properties Read more »

Argon atoms have 18 electrons and the shell structure is 2.8.8. The ground state electronic configuration of neutral Argon is [Ne].3s2.3p6 and the term symbol of Argon is 1S0.


Isolation: argon is present to a small extent in the atmosphere and is obtained as a byproduct from the liquefaction and separation of air. This would not normally be carried out in the laboratory and argon is available commercially in cylinders at high pressure.

Argon isotopes Read more »

Argon isotopes are used as precursors in the production of radioisotopes. Ar-40 and Ar-38 are used in the production of radioactive K-38 which can be used as a blood flow tracer. Ar-40 is used in the production of radioactive Ar-41 which is used to trace gas flows.

Table. Stables isotopes of argon.
Isotope Mass
(atom %)
spin (I)
moment (μ/μN)
36Ar 35.96754552 (29) 0.3365 (30) 0 0
38Ar 37.9627325 (9) 0.0632 (5) 0 0
40Ar 39.9623837 (14) 99.6003 (30) 0 0

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