xenon
From Glossary of Meteorology
(Symbol Xe.) A noble gas, atomic number 54, atomic weight 131.3; a heavy, unreactive, colorless element found in the atmosphere to the extent of only 0.0000087% by volume.
(Symbol Xe.) A noble gas, atomic number 54, atomic weight 131.3; a heavy, unreactive, colorless element found in the atmosphere to the extent of only 0.0000087% by volume.