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
First ionization energy / kJ mol-1:1520.58
Second ionization energy / kJ mol-1:2665.88
Third 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
Crystal structure:
face-centered cubic
Unit-cell dimensions / pm:
a=531.088
Space group:
Fm3m
| 17 Chlorine <= |
18 Argon
|
=> 19 Potassium |