Periodic Table


Atomic number: 36
Atomic weight: 83.80
Symbol: Kr
Group number: 18
Electronic configuration: [Ar].3d10.4s2.4p6


Krypton is present in the air at about 1 ppm. The atmosphere of Mars contains a little (about 0.3 ppm) of krypton. It is characterised by its brilliant green and orange spectral lines. The spectral lines of krypton are easily produced and some are very sharp. In 1960 it was internationally agreed that the fundamental unit of length, the metre, should be defined as 1 m = 1,650,763.73 wavelengths (in vacuo) of the orange-red line of Kr-33.

Under normal conditions krypton is colourless, odourless, fairly expensive gas. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases". Krypton difluoride, KrF2, has been prepared in gram quantities and can be made by several methods.

General information

Discoveror: Sir William Ramsay, Morris W. Travers
Date discovered: 1898
Discovered at: Greeat Britain
Meaning of name: From the Greek word "kryptos" meaning "hidden"

Physical data

Standard state: gas at 298 K
Colour: colourless
Density of solid at ambient temperature/kg m-3: no data
Molar volume/cm3: 27.99

Radii /pm

Atomic: 88
Covalent (single bond):
Pauling radius for the ion [Kr]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius72.982.921.9no data


Both values are quoted on the Pauling scale.

Pauling: 3.00
Allred Rochow: 2.94

Crystal Structure

structure: ccp (cubic close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 115.79
boiling point: 119.93

Enthalpies /kJ mol-1

fusion: 1.64
vaporization: 9.02

single bond enthalpies:
Kr-F Kr-Cl Kr-Br Kr-I Kr-Kr
50 no data no data no data 5.23

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
78Kr77.920396 (9)0.35 (2)
80Kr79.916380 (9)2.25 (2)
82Kr81.913482 (6)11.6 (1)
83Kr82.914135 (4)11.5 (1)
84Kr83.911507 (4)57.0 (3)
86Kr85.910616 (5)17.3 (2)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Kr.html