Editorial Feature

Krypton (Kr) - Discovery, Occurrence, Production, Properties and Applications of Krypton

Chemical Formula



With the aim of discovering the missing noble gases in the periodic table, Morris M. Travers and Sir William Ramsay studied liquefied air in 1898. Though the air was already known to contain 99.5% of oxygen, argon and nitrogen, it was difficult to identify the remaining 0.05%.

To identify the unknown part, the chemists first extracted a large volume of argon followed by nitrogen and oxygen using magnesium and red-hot copper. The remaining gas was placed in a vacuum tube to which a high voltage was applied for measuring the gas spectrum. As expected, they found argon gas in addition to two new lines in the spectrum, which was found to be a new element - krypton.

Basic Information

Name Krypton
Symbol Kr
Atomic number 36
Atomic weight 83.79 amu
Standard state Gas at 298 K
CAS Registry ID 7439-90-9
Group in periodic table 18
Group name Noble gas
Period in periodic table 4
Block in periodic table p-block
Color Colorless
Classification Non-metallic
Melting point 115.79 K (-157.36°C or -251.25°F)
Boiling point 119.93 K (-153.22°C or -243.8°F)
Density 0.0037 g/cm3
Phase at room temperature Gas


Traces of krypton of around 1 ppm are present in the atmosphere. Very small amount of krypton can also be formed in the Earth’s crust when uranium or other radioactive elements disintegrate.

Krypton - Periodic Table of Videos


Krypton has 33 known isotopes with mass numbers ranging from 69 to 101. Of these, six isotopes 78Kr, 80Kr, 82Kr, 83Kr, 84Kr and 86Kr occur naturally. The most abundant isotope in nature is 84Kr (57%) followed by 86Kr (17.3%), 82Kr (11.6%), 82Kr (11.5%), 80Kr (2.3%) and 78Kr (0.4%).


Krypton can be extracted by subjecting liquefied air to fractional distillation and removing carbon dioxide, nitrogen, water vapor and oxygen from the resulting residues of liquefied air.

Key Properties

The key properties of krypton are listed below:

  • It is a colorless, odorless, tasteless inert gas
  • Solid krypton is white and crystalline
  • It can react with fluoride.


Some of the applications of krypton include the following:

  • High-power, flashing airport runway lights
  • Krypton-based bulbs serve as excellent white light source for photographic flashes in high speed photography
  • It is used for manufacturing colorful neon lights.
  • It is used in MRI/CT techniques.


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G.P. Thomas

Written by

G.P. Thomas

Gary graduated from the University of Manchester with a first-class honours degree in Geochemistry and a Masters in Earth Sciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and turn his hand to writing. When he isn't developing topical and informative content, Gary can usually be found playing his beloved guitar, or watching Aston Villa FC snatch defeat from the jaws of victory.


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