500
How was Xenon discovered?
How is a large portion of the atmosphere was cooled down to a very low temperature and all the gases changed into liquid form, then the liquid was heated up; thus, it turned back into a gas. (Nitrogen, Oxygen, and Argon were the first gases to evaporate because they make up 99.5% of the atmosphere). The remaining liquid consisted of other atmospheric gases, one of which was Xenon.