The rare gases known variously as 'inert' or 'noble' gases for their stability and resistance to reaction were discovered in 1898 by William Ramsay and Morris Travers. They exist in the air, but because they are so unreactive, no-one had previously been able to isolate and identify them. The Scottish chemist Ramsay, and his assistant Travers, cooled air to the point at which it liquefies, and then used fractional distillation to separate the various gases of which it is made up. Argon had already recently been discovered, but they found the slightly more volatile neon, and the even more inert krypton and xenon. Ramsay was awarded the Nobel Prize for Chemistry in 1904 for these discoveries.
Editors. "Neon, krypton, and xenon discovered by William Ramsay and Morris Travers". The Literary Encyclopedia. First published 30 August 2013
[http://www.litencyc.com/php/stopics.php?rec=true&UID=6381, accessed 19 April 2014.]