Krypton



36 rubidium
Xe
General
Number krypton, Kr, 36
noble gases
Block p
Appearance colorless
(2)  g·mol−1
Ar] 3d10 4s2 4p6
shell 2, 8, 18, 8
Physical properties
Phase gas
Density (0 °C, 101.325 kPa)
3.749 g/L
F)
F)
K, 73.2 kPa[1]
K, 5.50 MPa
kJ·mol−1
kJ·mol−1
Heat capacity (25 °C) 20.786  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 59 65 74 84 99 120
Atomic properties
Crystal structure cubic face centered
Oxidation states 4,[2] 2
Electronegativity 3.00 (Pauling scale)
more) 1st:  1350.8  kJ·mol−1
2nd:  2350.4  kJ·mol−1
3rd:  3565  kJ·mol−1
Atomic radius (calc.) 88  pm
Covalent radius 110  pm
Van der Waals radius 202 pm
Miscellaneous
Magnetic ordering nonmagnetic
Thermal conductivity (300 K) 9.43x10-3  W·m−1·K−1
Speed of sound (gas, 23 °C) 220 m/s
Speed of sound (liquid) 1120 m/s
CAS registry number 7439-90-9
Selected isotopes
Main article: Isotopes of krypton
iso NA half-life DM DE (MeV) DP
78Kr 0.35% 2.3×1020 y ε ε - 78Se
79Kr syn 35.04 h ε - 79Br
β+ 0.604 79Br
γ 0.26, 0.39, 0.60 -
80Kr 2.25% Kr is neutrons
81Kr syn 2.29×105 y ε - 81Br
γ 0.281 -
82Kr 11.6% Kr is neutrons
83Kr 11.5% Kr is neutrons
84Kr 57% Kr is neutrons
85Kr syn 10.756 y β- 0.687 85Rb
86Kr 17.3% Kr is neutrons
References

Krypton (fluorine. Krypton can also form clathrates with water when atoms of it are trapped in a lattice of the water molecules.

From 1960 to 1983, the distance of the meter was defined in terms of the orange-red spectral line of krypton-86, an krypton fluoride laser.

Physical properties

 

Krypton is characterized by a brilliant crystal structure, which is a common property of all noble gases. The original name of krypton is "Hidden One." The melting point of krypton is -157.2 degrees Celsius, and its boiling point is -152.9 degrees Celsius.

History

Krypton (Greek κρυπτόν, kryptos meaning "hidden") was discovered in Great Britain in 1898 by noble gases, including krypton.

Metric role

In 1960, an international agreement defined the meter in terms of wavelength of light emitted by the krypton-86 isotope. This agreement replaced the longstanding standard iridium alloy (the bar was originally estimated to be one ten-millionth of a quadrant of the earth's polar circumference), and was itself replaced by a definition based on the speed of light — a fundamental physical constant. In October 1983, the Bureau International des Poids et Mesures (International Bureau of Weights and Measures) defined the meter as the distance that light travels in a vacuum during 1/299,792,458 s.[5]

Occurrence

The concentration of krypton in earth's fractional distillation.[6] The amount of krypton in space is uncertain, as is the amount is derived from the meteoritic activity and that from solar winds. The first measurements suggest an overabundance of krypton in space.[7]

Compounds

Like the other noble gases, krypton is chemically inert. However, following the first successful synthesis of Xe or KrXe+.[9]

At the University of Helsinki in Finland, HKrCN and HKrCCH (krypton hydride-cyanide and hydrokryptoacetylene) were synthesized and determined to be stable up to 40K (M. Räsänen et al.).[8]

If the kryptonite found in Superman stories followed the naming conventions of chemical compounds, it would be an oxyanion of krypton. Krypton cannot form an oxyanion.

Isotopes

Main article: isotopes of krypton

There are 31 known isotopes of krypton.[10] Naturally occurring krypton is made of five groundwater.[11]

85Kr is an inert radioactive noble gas with a half-life of 10.76 years. It is produced by the fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole as most nuclear reactors are in the northern hemisphere.[12]

Applications

Krypton's multiple emission lines make ionized krypton gas discharges appear white, which in turn makes krypton-based bulbs useful in photography as a brilliant white light source. Krypton is thus used in some types of photographic flashes used in high speed photography. Fluorescent light bulbs are filled with a mixture of krypton and argon gases. Krypton gas is also combined with other gases to make luminous signs that glow with a bright greenish-yellow light.[13]

Krypton's white discharge is often used to good effect in colored gas discharge tubes, which are then simply painted or stained in other ways to allow the desired color (for example, "neon" type advertising signs where the letters appear in differing colors, are often entirely krypton-based). Krypton is also capable of much higher light power density than neon in the red spectral line region, and for this reason, red lasers for high power laser light shows are krypton lasers with mirrors which select out the red spectral line for laser amplification and emission, rather than the more familiar helium-neon variety, which could never practically achieve the multi-watt red laser light outputs needed for this application.[14]

Krypton has an important role in production and usage of the laser has high beam uniformity, short wavelength, and the ability to modify the spot size to track an imploding pellet.[15]

In experimental particle physics, liquid krypton is used to construct quasi-homogenious electromagnetic calorimeters. A notable example is the calorimeter of the NA48 experiment at CERN containing about 27 tons of liquid krypton. This usage is rare, since the cheaper liquid argon is typically used. The advantage of krypton over agron is a small Molière radius of 4.7cm, which allows for excellent spatial resolution and low degree of overlapping. The other parameters relevant for calorimetry application are: radiation length of X0 = 4.7cm, density of 2.4g/cm³.

References

  1. ^ (2005) "Section 4, Properties of the Elements and Inorganic Compounds; Melting, boiling, triple, and critical temperatures of the elements", CRC Handbook of Chemistry and Physics, 85th edition, Boca Raton, Florida: CRC Press. 
  2. ^ Krypton: krypton(IV) fluoride compound data. Books.Google.com. Retrieved on 2007-12-10.
  3. ^ Krypton (English) 1. Argonne National Laboratory, EVS (08 2005). Retrieved on 2007-03-17.
  4. ^ William Ramsay, Morris W. Travers (1898). "On a New Constituent of Atmospheric Air". Proceedings of the Royal Society of London 63: 405-408.
  5. ^ Gibbs, Philip (1997). How is the speed of light measured? (English). Department of Mathematics, University of California. Retrieved on 2007-03-19.
  6. ^ How Products are Made: Krypton. Retrieved on 2006-07-02.
  7. ^ Cardelli, Jason A.; Meyer, David M. (18). The Abundance of Interstellar Krypton (English) 1-4. The American Astronomical Society. Retrieved on 2007-04-05.
  8. ^ a b Bartlett, Neil (2003). The Noble Gases (English). Chemical & Engineering News. Retrieved on 2006-07-02.
  9. ^ Periodic Table of the Elements (English) 100-101. Los Alamos National Laboratory's Chemistry Division. Retrieved on 2007-04-05.
  10. ^ Isotopes of Krypton. Nuclear Science Division. Retrieved on 2007-03-20.
  11. ^ Thonnard, Norbert; Larry D. MeKay, Theodore C. Labotka (31). Development of Laser-Based Resonance Ionization Techniques for 81-Kr and 85-Kr Measurements in the Geosciences (English) 4-7. University of Tennessee, Institute for Rare Isotope Measurements. Retrieved on 2007-03-20.
  12. ^ Resources on Isotopes. U.S. Geological Survey. Retrieved on 2007-03-20.
  13. ^ Mercury in Lighting. Cape Cod Cooperative Extension. Retrieved on 2007-03-20.
  14. ^ Laser Devices, Laser Shows and Effect (PDF). Retrieved on 2007-04-05.
  15. ^ Sethian, J.; M. Friedman, M.Myers. Krypton Fluoride Laser Development for Inertial Fusion Energy (English) 1-8. Plasma Physics Division, Naval Research Laboratory. Retrieved on 2007-03-20.

Further reading

  • Los Alamos National Laboratory - Krypton
  • "Chemical Elements: From Carbon to Krypton" By: David Newton & Lawrence W. Baker
  • "Krypton 85: a Review of the Literature and an Analysis of Radiation Hazards" By: William P. Kirk
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Krypton". A list of authors is available in Wikipedia.