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 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.
|Location||ppb by weight||ppb by atoms||Links|
|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 83.8 [‑189.3 °C (‑308.7 °F)] K
- Boiling point: 87.3 [‑185.8 °C (‑302.4 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
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.
- Pauling electronegativity: (no data) (Pauling units)
- First ionisation energy: 1520.6 kJ mol‑1
- Second ionisation energy: 2665.8 kJ mol‑1
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.
|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|