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Ar - Argon

Argon

 Argon 
Ar
Atomic Number: 18
Atomic Weight: 39.948
Element Type: Noble Gas
Crystal Structure: Cubic Face Centered
Melting Point: -189.35°C = -308.83°F = 83.8 K
Boiling Point: -185.85°C = -302.53°F = 87.3 K
Critical Temp: -122.28°C = -188.104°F = 150.87 K
Atomic Radius: 0.88 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 0.98 Å
Electronegativity:

History

(Gr. argos, inactive) Its presence in air was suspected by Cavendish in 1785,discovered by Lord Rayleigh and Sir William Ramsay in 1894.


Sources

The gas is prepared by fractionation of liquid air because the atmosphere contains0.94% argon. The atmosphere of Mars contains 1.6% of 40Ar and 5 p.p.m. of 36Ar.



Science Quote

'Our loyalties are to the species and the planet. We speak for Earth. Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring.'

Carl Sagan
(1934-1996)


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