krypton

(krĭp'tŏn')

[Greek krupton, neuter of kruptos, hidden (from its rarity), from kruptein, to hide.]

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Background

Krypton is chemical element number 36 on the periodic table of the elements. It belongs to the group of elements known as the noble gases. The other noble gases are helium, neon, argon, xenon, and radon. Under normal conditions, krypton is a colorless, tasteless, odorless gas. Its density at normal temperature and pressure is about 0.5 oz per gallon (3.7 g per liter), making it nearly three times heavier than air. At extremely low temperatures, krypton may exist as a liquid or a solid. The boiling point of krypton is -243.81° F (-153.23° C), and its freezing point is only slightly lower at -251.27° F (-157.37° C).

Natural krypton is a mixture of six stable isotopes. Isotopes are atoms which have the same number of protons but which have different numbers of neutrons. The number of protons (the atomic number) determines which element is present, while the total number of protons and neutrons determines the atomic weight of the atom. The isotopes of krypton all have 36 protons and are named for their atomic weights. Krypton-84, which has 48 neutrons, is the most common isotope and makes up 57% of natural krypton. The other stable isotopes of krypton are krypton-86 (50 neutrons, 17.3%); krypton-82 (46 neutrons, 11.6%); krypton-83 (47 neutrons, 11.5%); krypton-80 (44 neutrons, 2.25%); and krypton-78 (42 neutrons, 0.35%)

Krypton can also exist as an unstable, radioactive isotope. These isotopes are created during nuclear reactions. About 20 radioactive isotopes of krypton have been produced. All of these isotopes except krypton-85 are very unstable, with half-lives of a few hours or less. (The half-life of a radioactive substance is the time required for half of the atoms in a sample of the substance to undergo radioactive decay.) Krypton-85, which has 36 protons and 49 neutrons, is much more stable, with a half-life of 10.73 years.

Krypton is used with argon in fluorescent lights to improve their brightness and with nitrogen in incandescent lights to extend their lifetime. It is also used in flashbulbs to produce a very bright light for a very short period of time, for use in high-speed photography. Radioactive krypton-85 can be used to locate small flaws in metal surfaces. The gas tends to collect in these flaws and its radioactivity can be detected.

History

The noble gases were completely unknown to humanity until fairly recently. The first hint of their existence came in 1785, when the English chemist Henry Cavendish discovered that air contained a small amount of an unknown substance that was less reactive than nitrogen. Nothing else was known about this substance until the late nineteenth century.

Meanwhile, the British astronomer Joseph Norman Lockyer discovered a new element in 1868. By analyzing light from the sun, he detected an unknown element that he named helium, from the Greek word helios (sun). Helium was not known to exist on Earth for more than a quarter of a century.

In 1894, the English physicist Lord Rayleigh (John William Strutt) and the Scottish chemist William Ramsay discovered a difference in the density of nitrogen obtained from the air and nitrogen obtained from ammonia. They soon discovered that the atmospheric nitrogen was mixed with a small amount of an unknown substance. By using magnesium to absorb the nitrogen, they were able to isolate the substance, which they named argon, from the Greek word argos (inactive), because it did not react with other substances.

In 1895, Ramsay and his assistant Morris William Travers discovered that the mineral clevite released argon and helium when heated. This was the first time helium was detected on Earth. In 1898, Ramsay and Travers obtained three new elements from air, which had been cooled into a liquid. They named these elements krypton, from the Greek word kryptos (hidden); neon, from the Greek word neos (new); and xenon, from the Greek word xenos (strange).

In 1900, the German chemist Friedrich Dom noted that the radioactive element radium released helium and an unknown radioactive gas as it decayed. In 1910, Ramsay and his assistant Robert Whytlaw-Gray determined the density of this unknown gas and named it niton, from the Latin word nitere (to shine), because its radioactivity caused it to glow when cooled to a liquid. Niton, later known as radon, was the last noble gas to be discovered. In 1904, Ramsay was awarded the Nobel Prize in Chemistry for his research of noble gases.

The noble gases were formerly known as the rare gases or the inert gases. It was later shown that some were quite common and that some were not completely unreactive. Helium is the second most common element in the universe and argon makes up about 1% of Earth's atmosphere. In 1962, Neil Bartlett created xenon platinum hexafluoride, the first chemical compound of a noble gas. Compounds of radon were created in the same year and compounds of krypton in 1963. No longer thought of as rare or inert, these elements came to be known as the noble gases. Like the so-called noble metals (gold, silver, platinum, etc.), they did not react with oxygen.

Krypton played an important role in science from 1960-1983, when the length of the meter was defined as 1,650,763.73 times the wavelength of the orange-red light emitted by krypton-86. The meter was later defined in terms of the speed of light in a vacuum, but krypton continues to be used in scientific research.

Raw Mcaterials

Although traces of krypton are found in various minerals, the most important source of krypton is Earth's atmosphere. Air is also the most important source for the other noble gases, with the exception of helium (obtained from natural gas) and radon (obtained as a byproduct of the decay of radioactive elements). At sea level, dry air contains 78.08% nitrogen and 20.95% oxygen. It also contains 0.93% argon, 0.0018% neon, 0.00052% helium, 0.00011% krypton, and 0.0000087% xenon. Other components of dry air include carbon dioxide, hydrogen, methane, nitric oxide, and ozone.

Krypton can also be obtained from the fission of uranium, which occurs in nuclear power plants. Unlike air, which contains only the stable isotopes of krypton, this process produces both stable isotopes and radioactive isotopes of krypton.

The Manufacturing
Process

Making liquid air

• Air is first passed through filters to remove particulate matter such as dust. The clean air is then exposed to an alkali (a strongly basic substance), which removes water and carbon dioxide.
• The clean, dry air is compressed under high pressure. Because compression raises the temperature of the air, it is then cooled by refrigeration.
• The cooled, compressed air passes through coils winding through an empty chamber. A portion of the air, which is compressed to a pressure about two hundred times greater than normal, is allowed to expand into the chamber. This sudden expansion absorbs heat from the coils, cooling the compressed air. The process of compression and expansion is repeated until the air has been cooled to a temperature of about -321 F (-196° C), at which point most of the gases in the air are transformed into liquids.

Separating the gases

• Gases with very low boiling points are not transformed into liquids and can be removed from the others directly. These gases include helium, hydrogen, and neon.
• A process known as fractional distillation separates the various elements found in liquid air. This process relies on the fact that the different substances will be transformed from liquid to gas at different temperatures.
• The liquid air is allowed to warm slowly. As the temperature increases the substances with the lowest boiling points become gases and can be removed from the remaining liquid. Argon, oxygen, and nitrogen are the first substances to be transformed into gases as the liquid air warms. Krypton and xenon have higher boiling points and remain in the liquid state when the other components of air have become gases.

Separating krypton from xenon

• The liquid krypton and xenon are absorbed onto silica gel or onto activated charcoal. They are then once again subjected to fractional distillation. The liquid mixture is warmed slowly until the krypton is transformed into a gas. The xenon has a somewhat higher boiling point and remains behind as a liquid.
• The krypton is purified by passing it over hot titanium metal. This substance tends to remove all elements except noble gases.

Separating the isotopes of krypton

• For most purposes, the krypton is now ready to be packaged. For some scientific purposes, however, only one of the six stable isotopes of krypton is desired. To separate these isotopes, a process known as thermal diffusion is used. This process depends on the fact that the isotopes have slightly different densities.
• The krypton gas is placed in a long vertical glass tube. A heated wire runs vertically through the center of this tube. The hot wire sets up a convection current within the tube. This current of hot air tends to carry the lighter isotopes to the top of the tube, where they can be removed.

Packaging and shipping

• Krypton gas is packed in bulbs of a strong glass such as Pyrex at normal pressure or in steel canisters at high pressure. Because it is a highly unreactive substance, krypton is very safe. It is nontoxic, nonexplosive, and nonflammable, so it requires no unusual precautions during shipping.

Quality Control

The most important factor in the quality control of krypton production is ensuring that the final product contains only krypton. The process of fraction distillation has been developed to the point where it produces very pure products from air, including krypton.

Random samples of krypton are tested for purity by spectroscopic analysis. This process involves heating a substance until it emits light. The light then passes through a prism or a grating in order to produce a spectrum, in the same way that sunlight produces a rainbow. Spectroscopic analysis is particularly well suited to studying gases, because heated gases tend to produce sharp, bright lines on a spectrum of pure krypton, it is possible to tell if any impurities are present.

Byproducts/Waste

Krypton is only one of many valuable elements produced by the fractional distillation of liquid air. More than three-quarters of air is made up of nitrogen. Nitrogen is used to produce a wide variety of chemical compounds, particularly ammonia. Because it is much less reactive than oxygen, nitrogen is used to protect many substances from oxidation. Liquid nitrogen is used in freeze-drying and refrigeration.

About one-fifth of air consists of oxygen. The steel industry is the largest consumer of pure oxygen. Oxygen is used to remove excess carbon from steel in the form of carbon dioxide. Oxygen is also used to treat sewage and to incinerate solid waste. Liquid oxygen is used as rocket fuel.

The noble gases obtained from air other than krypton are argon, neon, and xenon. Argon is used in certain types of light bulbs. Passing an electric current through a glass tube containing neon under low pressure produces the familiar neon sign. Xenon is used in strobe lights to produce intense, short bursts of light.

The Future

The future production of krypton is likely to be influenced by the future of nuclear power production. Because krypton can be produced as a byproduct of nuclear fission, nuclear power plants may become an important source of krypton in the future. On the other hand, if nuclear fission is largely replaced by nuclear fusion or by other forms of energy production, krypton is likely to remain almost entirely a product of the atmosphere.

Where to Learn More

Books

Asimov, Isaac. The Noble Gases. Basic Books, 1966.

Atkins, P.W. The Periodic Kingdom: A Journey Into the Land of the Chemical Elements. Basic Books, 1995.

Compressed Gas Association. Handbook of Compressed Gases. Van Nostrand Reinhold, 1990.

[Article by: Rose Secrest]

A gaseous chemical element, Kr, atomic number 36, and atomic weight 83.80. Krypton is one of the noble gases in group 18 of the periodic table. Krypton is a colorless, odorless, and tasteless gas. The table gives some physical properties of krypton. The principal use for krypton is in filling electric lamps and electronic devices of various types. Krypton-argon mixtures are widely used to fill fluorescent lamps. See also Inert gases; Periodic table.

The only commercial source of stable krypton is the air, although traces of krypton are found in minerals and meteorites.

A mixture of stable and radioactive isotopes of krypton is produced in nuclear reactors by the slow-neutron fission of uranium. It is estimated that about 2 × 10⁻⁸% of the weight of the Earth is krypton. Krypton also occurs outside the Earth.

Lit With the Aid of Krypton

From our Archives: Today's Highlights, January 24, 2011

A chemical element, atomic number 36, atomic weight 83.80, symbol Kr.

One of the inert gases, present in small amounts in the atmosphere with an atomic number of 36 and an atomic weight of 83.80.

• Elements - krypton: Kr; atomic number 36, atomicweight 84

This article is about the chemical element. For other uses, see Krypton (disambiguation).

bromine ← krypton → rubidium Ar ↑ Kr ↓ Xe 36Kr Periodic table
Appearance
Colorless gas, exhibiting a whitish glow when placed in a high voltage electric field Spectral lines of Krypton
General properties
Name, symbol, number	krypton, Kr, 36
Pronunciation	/ˈkrɪptɒn/ KRIP-ton
Element category	noble gases
Group, period, block	18, 4, p
Standard atomic weight	83.798
Electron configuration	[Ar] 3d10 4s2 4p6
Electrons per shell	2, 8, 18, 8 (Image)
Physical properties
Phase	gas
Density	(0 °C, 101.325 kPa) 3.749 g/L
Liquid density at b.p.	2.413[1] g·cm−3
Melting point	115.79 K, -157.36 °C, -251.25 °F
Boiling point	119.93 K, -153.22 °C, -244.12 °F
Triple point	115.775 K (-157°C), 73.2 kPa
Critical point	209.41 K, 5.50 MPa
Heat of fusion	1.64 kJ·mol−1
Heat of vaporization	9.08 kJ·mol−1
Molar heat capacity	5R/2 = 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 74 120
Atomic properties
Oxidation states	2
Electronegativity	3.00 (Pauling scale)
Ionization energies	1st: 1350.8 kJ·mol−1
	2nd: 2350.4 kJ·mol−1
	3rd: 3565 kJ·mol−1
Covalent radius	116±4 pm
Van der Waals radius	202 pm
Miscellanea
Crystal structure	cubic face-centered
Magnetic ordering	diamagnetic[2]
Thermal conductivity	9.43x10-3  W·m−1·K−1
Speed of sound	(gas, 23 °C) 220, (liquid) 1120 m·s−1
CAS registry number	7439-90-9
Most stable isotopes
Main article: Isotopes of krypton
iso NA half-life DM DE (MeV) DP 78Kr 0.35% 78Kr is stable with 42 neutrons 79Kr syn 35.04 h ε - 79Br β+ 0.604 79Br γ 0.26, 0.39, 0.60 - 80Kr 2.25% 80Kr is stable with 44 neutrons 81Kr trace 2.29×105 y ε - 81Br γ 0.281 - 82Kr 11.6% 82Kr is stable with 46 neutrons 83Kr 11.5% 83Kr is stable with 47 neutrons 84Kr 57% 84Kr is stable with 48 neutrons 85Kr syn 10.756 y β− 0.687 85Rb 86Kr 17.3% 86Kr is stable with 50 neutrons
v t e · r

Krypton ( /ˈkrɪptɒn/ KRIP-ton; from Greek: κρυπτός kryptos "the hidden one") is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other rare gases in fluorescent lamps. Krypton is inert for most practical purposes.

Krypton, like the other noble gases, can be used in lighting and photography. Krypton light has a large number of spectral lines, and krypton's high light output in plasmas allows it to play an important role in many high-powered gas lasers (krypton ion and excimer lasers), which pick out one of the many spectral lines to amplify. There is also a specific krypton fluoride laser. The high power and relative ease of operation of krypton discharge tubes caused (from 1960 to 1983) the official length of a meter to be defined in terms of the red-orange spectral line of krypton-86.

Contents 1 History 2 Characteristics 2.1 Isotopes 2.2 Chemistry 2.3 Natural occurrence 3 Applications 4 Precautions 5 See also 6 References 7 Further reading 8 External links

History

Sir William Ramsay, the discoverer of krypton

Krypton was discovered in Britain in 1898 by Sir William Ramsay, a Scottish chemist, and Morris Travers, an English chemist, in residue left from evaporating nearly all components of liquid air. Neon was discovered by a similar procedure by the same workers just a few weeks later.^[3] William Ramsay was awarded the 1904 Nobel Prize in Chemistry for discovery of a series of noble gases, including krypton.

In 1960, an international agreement defined the meter in terms of wavelength of light emitted by the krypton-86 isotope (wavelength of 605.78 nanometers). This agreement replaced the longstanding standard meter located in Paris, which was a metal bar made of a platinum-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.^[4][5][6]

Characteristics

Krypton is characterized by several sharp emission lines (spectral signatures) the strongest being green and yellow.^[7] It is one of the products of uranium fission.^[8] Solidified krypton is white and crystalline with a face-centered cubic crystal structure, which is a common property of all noble gases (except helium, with a hexagonal close-packed crystal structure).

Isotopes

Main article: Isotopes of krypton

Naturally occurring krypton is made of six stable isotopes. In addition, about thirty unstable isotopes and isomers are known.^{[9] 81}Kr, the product of atmospheric reactions, is produced with the other naturally occurring isotopes of krypton. Being radioactive, it has a half-life of 230,000 years. Krypton is highly volatile when it is near surface waters but ⁸¹Kr has been used for dating old (50,000–800,000 years) groundwater.^[10]

⁸⁵Kr is an inert radioactive noble gas with a half-life of 10.76 years. It is produced by the fission of uranium and plutonium, such as in nuclear bomb testing and nuclear reactors. ⁸⁵Kr is released during the reprocessing of fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole due to convective mixing.^[11]

Chemistry

Like the other noble gases, krypton is chemically unreactive. However, following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride (KrF₂) was reported in 1963.^[12] In the same year, KrF₄ was reported by Grosse, et al.,^[13] but was subsequently shown to be a mistaken identification.^[14] There are also unverified reports of a barium salt of a krypton oxoacid.^[15] ArKr⁺ and KrH⁺ polyatomic ions have been investigated and there is evidence for KrXe or KrXe⁺.^[16]

Compounds with krypton bonded to atoms other than fluorine have also been discovered. The reaction of KrF₂ with B(OTeF₅)₃ produces an unstable compound, Kr(OTeF₅)₂, that contains a krypton-oxygen bond. A krypton-nitrogen bond is found in the cation [HC≡N–Kr–F]+
, produced by the reaction of KrF₂ with [HC≡NH]+
[AsF−
6] below −50 °C.^[17][18] HKrCN and HKrC≡CH (krypton hydride-cyanide and hydrokryptoacetylene) were reported to be stable up to 40 K.^[12]

Natural occurrence

The Earth has retained all of the noble gases that were present at its formation except for helium. Krypton's concentration in the atmosphere is about 1 ppm. It can be extracted from liquid air by fractional distillation.^[19] The amount of krypton in space is uncertain, as the amount is derived from the meteoric activity and that from solar winds. The first measurements suggest an overabundance of krypton in space.^[20]

Applications

Krypton gas discharge tube

Krypton discharge (spectrum) tube

Krypton's multiple emission lines make ionized krypton gas discharges appear whitish, 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. Krypton gas is also combined with other gases to make luminous signs that glow with a bright greenish-yellow light.^[21]

Krypton mixes with argon as the fill gas of energy saving fluorescent lamps. This reduces their power consumption. Unfortunately this also reduces their light output and raises their cost.^[22] Krypton costs about 100 times as much as argon. Krypton (along with xenon) is also used to fill incandescent lamps to reduce filament evaporation and allow higher operating temperatures to be used for the filament.^[23] A brighter light results which contains more blue than conventional lamps.

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 often 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.^[24]

Krypton has an important role in production and usage of the krypton fluoride laser. The laser has been important in the nuclear fusion energy research community in confinement experiments. The laser has high beam uniformity, short wavelength, and the ability to modify the spot size to track an imploding pellet.^[25]

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

The sealed spark gap assemblies contained in ignition exciters used in some older jet engines contain a very small amount of Krypton-85 to obtain consistent ionization levels and uniform operation.

Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways. In particular, it may be used to distinguish between hydrophobic and hydrophilic surfaces containing an airway.^[26]

Although xenon has potential for use in computed tomography (CT) to assess regional ventilation, its anesthetic properties limit its fraction in the breathing gas to 35%. The use of a breathing mixture containing 30% xenon and 30% krypton is comparable in effectiveness for CT to a 40% xenon fraction, while avoiding the unwanted effects of a high fraction xenon gas.^[27]

Precautions

Krypton is considered to be a non-toxic asphyxiant.^[28] Krypton has a narcotic potency seven times greater than air, so breathing a gas containing 50% krypton and 50% air would cause narcosis similar to breathing air at four times atmospheric pressure. This would be comparable to scuba diving at a depth of 30 m (100 ft) (see nitrogen narcosis) and potentially could affect anyone breathing it. Nevertheless, that mixture would contain only 10% oxygen and hypoxia would be a greater concern.

See also

Books View or order collections of articles	Krypton Period 4 elements Noble gases Chemical elements (sorted alphabetically) Chemical elements (sorted by number)
Portals Access related topics	Chemistry portal
Find out more on Wikipedia's Sister projects	Images and media from Commons Definitions from Wiktionary Learning resources from Wikiversity

References

1. ^ [1]
2. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
3. ^ William Ramsay, Morris W. Travers (1898). "On a New Constituent of Atmospheric Air". Proceedings of the Royal Society of London 63 (1): 405–408. doi:10.1098/rspl.1898.0051. 
4. ^ Shri Krishna Kimothi (2002). The uncertainty of measurements: physical and chemical metrology: impact and analysis. American Society for Qualit. p. 122. ISBN 0873895355. http://books.google.com/books?id=ckyqWMwJXJMC&pg=PA122. 
5. ^ Gibbs, Philip (1997). "How is the speed of light measured?". Department of Mathematics, University of California. http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html. Retrieved 2007-03-19. 
6. ^ Unit of length (meter), NIST
7. ^ "Spectra of Gas Discharges". http://astro.u-strasbg.fr/~koppen/discharge/. 
8. ^ "Krypton". Argonne National Laboratory, EVS. 2005. http://www.ead.anl.gov/pub/doc/krypton.pdf. Retrieved 2007-03-17. 
9. ^ Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. 
10. ^ 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". University of Tennessee, Institute for Rare Isotope Measurements. pp. 4–7. http://www.osti.gov/bridge/servlets/purl/809813-0zMCV1/native/809813.pdf. Retrieved 2007-03-20. 
11. ^ "Resources on Isotopes". U.S. Geological Survey. http://wwwrcamnl.wr.usgs.gov/isoig/period/kr_iig.html. Retrieved 2007-03-20. 
12. ^ ^{a b} Bartlett, Neil (2003). "The Noble Gases". Chemical & Engineering News. http://pubs.acs.org/cen/80th/noblegases.html. Retrieved 2006-07-02. 
13. ^ Grosse, A. V.; Kirshenbaum, A. D.; Streng, A. G.; Streng, L. V. (1963). "Krypton Tetrafluoride: Preparation and Some Properties". Science 139 (3559): 1047–1048. Bibcode 1963Sci...139.1047G. doi:10.1126/science.139.3559.1047. PMID 17812982.  edit
14. ^ Prusakov, V. N.; Sokolov, V. B. (1971). "Krypton difluoride". Soviet Atomic Energy 31 (3): 990–999. doi:10.1007/BF01375764.  edit
15. ^ Streng, A.; Grosse, A. (1964). "Acid of Krypton and Its Barium Salt". Science 143 (3603): 242–243. Bibcode 1964Sci...143..242S. doi:10.1126/science.143.3603.242. PMID 17753149.  edit
16. ^ "Periodic Table of the Elements". Los Alamos National Laboratory's Chemistry Division. pp. 100–101. Archived from the original on November 25, 2006. http://web.archive.org/web/20061125134307/http://www.bu.edu/ehs/ih/pdf/periodic_table.pdf. Retrieved 2007-04-05. 
17. ^ John H. Holloway; Eric G. Hope (1998). A. G. Sykes. ed. Advances in Inorganic Chemistry. Academic Press. pp. 57. ISBN 012023646X. 
18. ^ Errol G. Lewars (2008). Modeling Marvels: Computational Anticipation of Novel Molecules. Springer. p. 68. ISBN 1402069723. http://books.google.com/?id=whdw2qlXjD0C. 
19. ^ "How Products are Made: Krypton". http://www.madehow.com/Volume-4/Krypton.html. Retrieved 2006-07-02. 
20. ^ Cardelli, Jason A.; Meyer, David M. (1996). "The Abundance of Interstellar Krypton". The Astrophysical Journal Letters. The American Astronomical Society. pp. L57–L60. http://www.journals.uchicago.edu/doi/full/10.1086/310513. Retrieved 2007-04-05. 
21. ^ "Mercury in Lighting". Cape Cod Cooperative Extension. Archived from the original on September 29, 2007. http://web.archive.org/web/20070929085332/http://www.capecodextension.org/pdfs/Mercury+Lighting.pdf. Retrieved 2007-03-20. 
22. ^ "Energy-saving" lamps
23. ^ Properties, Applications and Uses of the "Rare Gases" Neon, Krypton and Xenon
24. ^ "Laser Devices, Laser Shows and Effect" (PDF). http://www.gameops.com/content/pdf/laser_terms.pdf. Retrieved 2007-04-05. 
25. ^ Sethian, J.; M. Friedman, M.Myers. "Krypton Fluoride Laser Development for Inertial Fusion Energy". Plasma Physics Division, Naval Research Laboratory. pp. 1–8. http://aries.ucsd.edu/LIB/MEETINGS/IAEAIFECRP/PDF/Sethian.pdf. Retrieved 2007-03-20. 
26. ^ Pavlovskaya, GE; Cleveland, ZI; Stupic, KF; Basaraba, RJ; Meersmann, T (2005). "Hyperpolarized krypton-83 as a contrast agent for magnetic resonance imaging". Proceedings of the National Academy of Sciences U.S.A. 102 (51): 18275–9. Bibcode 2005PNAS..10218275P. doi:10.1073/pnas.0509419102. PMC 1317982. PMID 16344474. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1317982. 
27. ^ Chon, D; Beck, KC; Simon, BA; Shikata, H; Saba, OI; Hoffman, EA (2007). "Effect of low-xenon and krypton supplementation on signal/noise of regional CT-based ventilation measurements". Journal of Applied Physiology 102 (4): 1535–44. doi:10.1152/japplphysiol.01235.2005. PMID 17122371. 
28. ^ Properties of Krypton

Further reading

• William P. Kirk "Krypton 85: a Review of the Literature and an Analysis of Radiation Hazards", Environmental Protection Agency, Office of Research and Monitoring, Washington (1972)

External links

• Krypton Fluoride Lasers, Plasma Physics Division Naval Research Laboratory

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Alkali metals Alkaline earth metals Lanthanides Actinides Transition metals Post-transition metals Metalloids Other nonmetals Halogens Noble gases Unknown chem. properties
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Dansk (Danish)
n. - krypton

Nederlands (Dutch)
krypton

Français (French)
n. - krypton

Deutsch (German)
n. - Krypton

Ελληνική (Greek)
n. - (χημ.) κρυπτό(ν)

Italiano (Italian)
cripto

Português (Portuguese)
n. - tipo de gás (m), elemento químico encontrado no ar

Русский (Russian)
криптон

Español (Spanish)
n. - criptón

Svenska (Swedish)
n. - krypton

中文（简体）(Chinese (Simplified))
氪

中文（繁體）(Chinese (Traditional))
n. - 氪

한국어 (Korean)
n. - 불활성 회유 원소(크립톤)

日本語 (Japanese)
n. - クリプトン

العربيه (Arabic)
‏(الاسم) عنصر غازي عديم اللون‏

עברית (Hebrew)
n. - ‮קריפטון (כימיה), יסוד מקבוצת הגזים האצילים‬

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