an inert, monatomic gaseous element, present in very small amounts in the atmosphere: used in high-power, tungsten-filament light bulbs. Symbol: Kr; atomic weight: 83.80; atomic number: 36.
a heavy, colorless, chemically inactive, monatomic gaseous element used for filling radio, television, and luminescent tubes. Symbol: Xe; atomic weight: 131.30; atomic number: 54.
