Krypton

Krypton - Kr

CAS:7439-90-9
Description: Colorless, odorless, tasteless gas
Classification: Noble Gas
Date of Discovery: 1898
Discoverer: Sir William Ramsey
Name Origin: Greek kryptos, "hidden"

Atomic Number: 36
Number of Neutrons: 48
Atomic Mass: 83.80(1) amu
Melting Point: -157.36 °C
Boiling Point: -153.22 ± 0.10 °C
Density @ 0 °C: 3.733 g/cm³
Atomic volume: 38.9 cm³/mol
Electrical resistivity: 0.630 10^-6/cm

Thermal conductivity: 0.0000949 W/cmK
Enthalpy of atomization:
Enthalpy of vaporization: 9.029 kJ/mol
Enthalpy of fusion: 1.638 kJ/mol
Specific heat capacity: 0.248 J/gK

Energy levels: 2-8-18-8
Electron configuration: [Ar]3d¹⁰4s²4p⁶
Crystal Structure: Cubic face centered
Atomic radius: 1.03 Å
Covalent radius: 1.12 Å
Oxidation States: usually 0
Electronegativity, Pauling:
Electron affinity: not stable
First ionization energy: 13.999 eV
2nd ionization energy: 24.359 eV
3rd ionization energy: 36.95 eV
Polarizability: 2.4844 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
⁷¹Kr	70.9505	0.10 s	⁺, EC
⁷²Kr	71.9419	17 s	⁺; EC	0+
⁷³Kr	72.9389	27 s	⁺; EC; ⁺, p
⁷⁴Kr	73.9333	11.5 m	⁺; EC	0+
⁷⁵Kr	74.93104	4.3 m	⁺; EC
⁷⁶Kr	75.92595	14.8 h	EC	0+
⁷⁷Kr	76.92467	1.24 h	⁺; EC	5/2 +
⁷⁸Kr	0.35(2)	77.92309	Stable	0+
^79mKr	53 s	IT	7/2+
⁷⁹Kr	78.920083	⁺; EC	1/2-
⁸⁰Kr	2.25(2)	79.916379	Stable	0+
^81mKr	13.1 s	IT	1/2-
⁸¹Kr	80.916593	2.1 x 10⁵ y	EC	7/2+
⁸²Kr	11.6(1)	81.913485	Stable	0+
^83mKr	1.86 h	IT	1/2-
⁸³Kr	11.5(1)	82.914137	Stable	9/2+
⁸⁴Kr	57.0(3)	83.911508	Stable	^-
^85mKr	4.48 h	^-; IT	1/2-
⁸⁵Kr	84.912530	10.73 y	^-	9/2+
⁸⁶Kr	17.3(2)	85.910615	Stable	0+
⁸⁷Kr	86.913359	1.27 h	^-	5/2+
⁸⁸Kr	87.91445	2.84 h	^-	0+
⁸⁹Kr	88.91764	3.15 m	^-	5/2+
⁹⁰Kr	89.91953	32.3 s	^-	0+
⁹¹Kr	90.9234	8.6 s	^-	5/2+
⁹²Kr	91.92611	1.84 s	^-; n
⁹³Kr	92.9312	1.29 s	^-; n
⁹⁴Kr	93.9343	0.21 s	^-
⁹⁵Kr	94.9397	0.78 s	^-
⁹⁷Kr	<0.1 s	^-
Discovered in 1898 by Ramsay and Travers in the residue left after liquid air had nearly boiled away. Krypton is present in the air to the extent of about 1 ppm. The atmosphere of Mars has been found to contain 0.3 ppm of krypton. It is one of the "noble" gases. It is characterized by its brilliant green and orange spectral lines. Naturally occurring krypton contains six stable isotopes. Twenty-four other unstable isotopes and isomers are now recognized. 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 meter, should be defined in terms of the orange-red spectral line of Kr. This replaced the standard meter of Paris, which was defined in terms of a bar made of a platinum-iridium alloy. In October 1983 the meter, which originally was defined as being one ten millionth of a quadrant of the earth's polar circumference, was again redefined by the International Bureau of Weights and Measures as being the length of a path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases." While krypton is generally thought of as a rare gas that normally does not combine with other elements to form compounds, it now appears that the existence of some krypton compounds is established. Krypton difluoride has been prepared in gram quantities and can be made by several methods. A higher fluoride of krypton and a salt of an oxyacid of krypton also have been reported. Molecule-ions of ArKr⁺ and KrH⁺ have been identified and investigated, and evidence is provided for the formation of KrXe or KrXe⁺. Krypton clathrates have been prepared with hydroquinone and phenol. ⁸⁵Kr has found recent application in chemical analysis. By imbedding the isotope in various solids, kryptonates are formed. The activity of these kryptonates is sensitive to chemical reactions at the surface. Estimates of the concentration of reactants are therefore made possible. Krypton is used in certain photographic flash lamps for high-speed photography. Uses thus far have been limited because of its high cost. LINKS: Krypton Generator Krypton Laser Resurfacing Photon Interaction Coefficients of Krypton Spectra of Krypton Gas Discharge Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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