Relative atomic mass: 4.002602 +- 0.000002

English: Helium
French: Helium
Croatian: Helij
German: Helium
Italian: Elio
Spanish: Helio

Atomic number: 2
Group numbers: 18
Period: 1
Standard state (20 oC): gas

Discovery: 1868 Pierre Jules Cesar Janssen (FR); Sir Joseph Norman Lockyer (GB)
Helium was discovered by Pierre Jules Cesar Janssen (FR) and Sir Joseph Norman Lockyer (GB) in 1868. The origin of the name comes from the Greek word helios meaning sun. It is a light, odourless, colourless inert gas. Helium is the second most abundant element in the universe. Helium is found in natural gas deposits from wells in Texas, Oklahoma and Kansas. It is used in balloons, deep sea diving and welding and in very low temperature research. The price of 99.999 % pure helium gas costs 177.10 /dm3 in small quantities (1 dm3) and about 2.52 /dm3 in large quantities (300 dm3).
Electronic configuration: 1s2
Formal oxidation number: 0
Atomic radius: 128 pm

Electronegativities: -
Thermal conductivity: 0.155 W/(m K)
Electrical resistivity (20 oC): - microOhm cm

Melting point: -272.2 oC
Boiling point: -268.93 oC

Heat of fusion: 0.021 kJ/mol
Heat of vaporization: 0.082 kJ/mol
Heat of atomization: 0 kJ/mol

1H <= 2He => 3Li

ASCII Periodic Table of the Elements
6 Jan. 2020
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