Krypton (Kr)

Stable isotopes of krypton available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Kr-78 36 42 77.92039 0.35% 99.90% Gas
Kr-80 36 44 79.916379 2.25% 99.90% Gas
Kr-82 36 46 81.913485 11.60% 99.90% Gas
Kr-83 36 47 82.914137 11.50% 99.90% Gas
Kr-84 36 48 83.911508 57.00% 99.90% Gas
Kr-86 36 50 85.910615 17.30% 99.90% Gas

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Krypton was discovered in 1898 by Sir William Ramsay and Morris W. Travers. Its name originates with the Greek word kryptos, meaning “hidden.”

Krypton is a colorless, odorless, tasteless gas. It liquefies at -153.22 ºC and solidifies at 157.36 ºC to a white crystalline substance with a face-centered cubic structure. It is slightly soluble in water.

Krypton is an inert gas element. Its closed-shell, stable octet electron configuration allows zero reactivity with practically any substance. Only a few types of compounds, complexes and clathrates have been synthesized, mostly with fluorine, the most electronegative element.

The commercial applications of krypton are fewer than those of helium or argon. Its principal use is in fluorescent lights. It is mixed with argon as a filling gas to enhance brightness in fluorescent tubes. Other applications are in flash tubes for high-speed photography and incandescent bulbs. Radioactive Krypton-85 is used as a tracer to monitor surface reactions. The unit of length “meter” was once defined in terms of the orange-red spectral line of Krypton-86.

Properties of Krypton

Name Krypton
Symbol Kr
Atomic number 36
Atomic weight 83.30
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 Nonmetallic
Melting point -157.36 °C
Boiling point -153.22 °C
Thermal conductivity 0.00943 W/(m·K)
Electronegativity 3.00
Heat of vaporization 9.02 kJ·mol-1
Heat of fusion 1.64 kJ·mol-1
Density of gas .0037 g/cm3
Density of liquid No data available
Density of solid 2.16 g/cm3
Electron configuration [Ar]3d104s24p6
First ionization potential 13.999 volts
Oxidation state  0 (an uncommon oxidation state +2 exists for its difluoride)
Critical temperature -63.7 ºC
Critical pressure 54.30 atm
Critical density 0.908 g/L