Atomic number:18

Group numbers:18

Period:3

Electronic configuration:[Ne] 3s² 3p⁶

Formal oxidation number:0

Electronegativities:-

Atomic radius / pm:188

Relative atomic mass:39.948 ± 0.001

 

Argon was discovered by Lord Raleigh and Sir William Ramsay (GB) in 1894. The origin of the name comes from the Greek word argos meaning inactive. It is a colourless and odourless noble gas, chemically inert. Argon is the third most abundant element in the earth's atmosphere and makes up about 1%. Argon is continuously released into the air by decay of radioactive potassium-40. Pure form is obtained from fractional distillation of liquid air. It is used in lighting products, and is often used in filling incandescent light bulbs. Some is mixed with krypton in fluorescent lamps. Crystals in the semiconductor industry are grown in argon atmospheres.

Density / g dm^-3:1656 (40 K)

 1.784 (273 K)

Molar volume / cm³mol^-1:24.12 (40 K)

 22392.38 (273 K)

Electrical resistivity / μΩcm:- (20 °C)

Thermal conductivity / W m^-1K^-1:0.0179

Melting point / °C:-189.34

Boiling point / °C:-185.89

Heat of fusion / kJ mol^-1:1.21

Heat of vaporization / kJ mol^-1:6.53

Heat of atomization / kJ mol^-1:0

1st ionization energy / kJ mol^-1:1520.58

2nd ionization energy / kJ mol^-1:2665.88

3rd ionization energy / kJ mol^-1:3930.84

in the atmosphere / ppm:9300

in the Earth's crust / ppm:1.2

in the oceans / ppm:0.6