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This is krypton.

Symbol Kr
Atomic number 36
Atomic mass 83.80 amu

Krypton was discovered in 1898 when liquefied atmospheric gases were carefully analyzed. Up until this time, only helium (1868) and argon (1894) had been discovered. But because of their wide difference in atomic masses of (atomic mass = 4.0026 amu for helium and (atomic mass = 39.948 amu for argon), it was suspected that more gaseous elements belonging to this group of gases existed. The cold residues that remained after the liquid helium and argon were drawn off were carefully examined. Using fractional distillation, this experiment yielded the discovery of a new noble gas, krypton. Its name is from the Greek word, kryptos, meaning "hidden". This method, incidentally, was also used to discover neon a few weeks later.

Distinguishing properties

Krypton is a dense, colorless, odorless atmospheric gas. It ranks seventh on the list of gases in the earth's atmosphere. Today, the gas is still captured and separated for commercial and laboratory applications by fractional distillation of liquid air. Shown to the right is the glow discharge of krypton gas.


None of the naturally occurring isotopes of krypton is radioactive. The radioactive isotopes of krypton are produced artificially as byproducts of nuclear power plants. It is used to keep track of Soviet nuclear production by subtracting off the amount that is generated from the reactors of the Western world from the total in the air.

  • Krypton-85 is used as a low-cost source of radiation for industrial thickness gauges and leak-testing instruments.
  • The International Committee of Weights and Measures once used Krypton-86 as the basis of the international definition of a meter. The meter was once defined in terms of the vacuum wavelength of the radiation corresponding to the transition between two atomic levels of the krypton isotope.


The commercial applications of kryton include its use as inert filler-gas in incandescent bulbs, and fluorescent lamps. The most important application is in the flashing stroboscopic lamps that light up airport runways during hours of darkness.

As for Superman's strength-zapping nemesis, kryptonite, the resemblance of the name to krypton the element is purely coincidental.

See also

Periodic table of the elements