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Kr - Krypton

Krypton

 Krypton 
Kr
Atomic Number: 36
Atomic Weight: 83.8
Element Type: Noble Gas
Crystal Structure: Cubic Face Centered
Melting Point: -157.36°C = -251.248°F = 115.79 K
Boiling Point: -153.22°C = -243.796°F = 119.93 K
Critical Temp: -63.74°C = -82.732°F = 209.41 K
Atomic Radius: 1.03 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 1.12 Å
Electronegativity:

History

(Gr. kryptos, hidden) Discovered in 1898 by Ramsay and Travers in the residue leftafter liquid air had nearly boiled away. In 1960 it was internationally agreed that thefundamental unit of length, the meter, should be defined in terms of the orange-redspectral line of 86Kr. This replaced the standard meter of Paris, which was defined interms of a bar made of a platinum-iridium alloy. In October 1983 the meter, whichoriginally was defined as being one ten millionth of a quadrant of the earth's polarcircumference, was again redefined by the International Bureau of Weights and Measures asbeing the length of a path traveled by light in a vacuum during a time interval of1/299,792,458 of a second.


Sources

Krypton is present in the air to the extent of about 1 ppm. The atmosphere of Mars hasbeen found to contain 0.3 ppm of krypton. Solid krypton is a white crystalline substancewith a face-centered cubic structure which is common to all the "rare gases."







Science Quote

'I beseech you to take interest in these sacred domains so expressively called laboratories. Ask that there be more and that they be adorned for these are the temples of the future, wealth and well-being. It is here that humanity will grow, strengthen and improve. Here, humanity will learn to read progress and individual harmony in the works of nature, while humanity's own works are all too often those of barbarism, fanaticism and destruction.'

Louis Pasteur
(1822-1895)





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