Krypton

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Krypton, 36Kr
A krypton-filled discharge tube glowing white
Krypton
Pronunciation/ˈkrɪptɒn/ (KRIP-ton)
Appearancecolorless gas, exhibiting a whitish glow in an electric field
Standard atomic weight Ar°(Kr)
Krypton in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ar

Kr

Xe
brominekryptonrubidium
kJ/mol
Heat of vaporization9.08 kJ/mol
Molar heat capacity20.95[6] J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 59 65 74 84 99 120
Atomic properties
Discovery and first isolation
William Ramsay and Morris Travers (1898)
Isotopes of krypton
Main isotopes[10] Decay
abun­dance half-life (t1/2) mode pro­duct
78Kr 0.360% 9.2×1021 y[11] εε
78Se
79Kr synth 35 h ε
79Br
β+
79Br
γ
80Kr 2.29%
stable
81Kr trace 2.3×105 y ε
81Br
81mKr synth 13.10 s
IT
81Kr
ε 81Br
82Kr 11.6% stable
83Kr 11.5% stable
84Kr 57.0% stable
85Kr trace 11 y
β
85Rb
86Kr 17.3% stable
 Category: Krypton
| references

Krypton (from

atmosphere and is often used with other rare gases in fluorescent lamps. Krypton is chemically inert
.

Krypton, like the other noble gases, is used in lighting and

discharge tubes
.

History

Sir William Ramsay, the discoverer of krypton

Krypton was discovered in Britain in 1898 by 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.[12] William Ramsay was awarded the 1904 Nobel Prize in Chemistry for discovery of a series of noble gases, including krypton.[13]

In 1960, the

ångström based on the red cadmium spectral line,[16] replacing it with 1 Å = 10−10 m. The krypton-86 definition lasted until the October 1983 conference, which redefined the meter as the distance that light travels in vacuum during 1/299,792,458 s.[17][18][19]

Characteristics

Krypton is characterized by several sharp emission lines (

cubic crystal structure, which is a common property of all noble gases (except helium, which has a hexagonal close-packed crystal structure).[22]

Isotopes

Naturally occurring krypton in Earth's atmosphere is composed of five

radioactive with a half-life of 230,000 years. Krypton is highly volatile and does not stay in solution in near-surface water, but 81Kr has been used for dating old (50,000–800,000 years) groundwater.[25]

fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole due to convective mixing.[26]

Chemistry

Like the other noble gases, krypton is chemically highly unreactive. The rather restricted chemistry of krypton in the +2 oxidation state parallels that of the neighboring element

scandide contraction it is difficult to oxidize the 4p elements to their group oxidation states. Until the 1960s no noble gas compounds had been synthesized.[27]

Following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride (KrF
2
) was reported in 1963. In the same year, KrF
4
was reported by Grosse, et al.,[28] but was subsequently shown to be a mistaken identification.[29] Under extreme conditions, krypton reacts with fluorine to form KrF2 according to the following equation:

Krypton gas in a

complex in an excited energy state:[30]

The complex can undergo spontaneous or stimulated emission, reducing its energy state to a metastable, but highly repulsive ground state. The ground state complex quickly dissociates into unbound atoms:

The result is an exciplex laser which radiates energy at 248 nm, near the ultraviolet portion of the spectrum, corresponding with the energy difference between the ground state and the excited state of the complex.[31]

Kr(H2)4 and H2 solids formed in a diamond anvil cell[32]
Structure of Kr(H2)4. Krypton octahedra (green) are surrounded by randomly oriented hydrogen molecules.[32]

Compounds with krypton bonded to atoms other than

polyatomic ions have been investigated and there is evidence for KrXe or KrXe+.[34]

The reaction of KrF
2
with B(OTeF
5
)
3
produces an unstable compound, Kr(OTeF
5
)
2
, that contains a krypton-

cation [HC≡N–Kr–F]+
, produced by the reaction of KrF
2
with [HC≡NH]+
[AsF
6
] below −50 °C.[35][36] HKrCN and HKrC≡CH (krypton hydride-cyanide and hydrokryptoacetylene) were reported to be stable up to 40 K.[27]

Krypton hydride (Kr(H2)4) crystals can be grown at pressures above 5 GPa. They have a face-centered cubic structure where krypton octahedra are surrounded by randomly oriented hydrogen molecules.[32]

Natural occurrence

Earth has retained all of the noble gases that were present at its formation except

ppm. It can be extracted from liquid air by fractional distillation.[37] The amount of krypton in space is uncertain, because measurement is derived from meteoric activity and solar winds. The first measurements suggest an abundance of krypton in space.[38]

Applications

Krypton gas discharge 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 white light source. Krypton is used in some photographic flashes for high speed photography. Krypton gas is also combined with mercury to make luminous signs that glow with a bright greenish-blue light.[39]

Krypton is mixed with argon in energy efficient fluorescent lamps, reducing the power consumption, but also reducing the light output and raising the cost.[40] 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.[41]

Krypton's white discharge is sometimes used as an artistic effect in gas discharge "neon" tubes. Krypton produces much higher light power 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 that select the red spectral line for laser amplification and emission, rather than the more familiar helium-neon variety, which could not achieve the same multi-watt outputs.[42]

The krypton fluoride laser is important in nuclear fusion energy research in confinement experiments. The laser has high beam uniformity, short wavelength, and the spot size can be varied to track an imploding pellet.[43]

In experimental

NA48 experiment at CERN containing about 27 tonnes of liquid krypton. This usage is rare, since liquid argon is less expensive. The advantage of krypton is a smaller Molière radius of 4.7 cm, which provides excellent spatial resolution with little overlapping. The other parameters relevant for calorimetry are: radiation length
of X0=4.7 cm, and density of 2.4 g/cm3.

Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways. In particular, it enables the radiologist to distinguish between hydrophobic and hydrophilic surfaces containing an airway.[44]

Although xenon has potential for use in

spent fuel when the cladding is removed.[49]

Krypton is used occasionally as an insulating gas between window panes.[50] SpaceX Starlink uses krypton as a propellant for their electric propulsion system.[51]

Precautions

Krypton compared to other anaesthetic gases (minimum alveolar concentration is an inverse indicator of potency)

Krypton is considered to be a non-toxic

lipophilic, krypton has a significant anaesthetic effect (although the mechanism of this phenomenon is still not fully clear,[53] there is good evidence that the two properties are mechanistically related), with narcotic potency seven times greater than air, and breathing an atmosphere of 50% krypton and 50% natural air (as might happen in the locality of a leak) causes narcosis
in humans similar to breathing air at four times atmospheric pressure. This is comparable to scuba diving at a depth of 30 m (100 ft) and could affect anyone breathing it.

References

  1. ^ "Standard Atomic Weights: Krypton". CIAAW. 2001.
  2. ISSN 1365-3075
    .
  3. ^ Krypton. encyclopedia.airliquide.com
  4. ^ "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 ed.). Boca Raton, Florida: CRC Press. 2005.
  5. ^ .
  6. ^ Shuen-Chen Hwang, Robert D. Lein, Daniel A. Morgan (2005). "Noble Gases". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. pp. 343–383. doi:10.1002/0471238961.0701190508230114.a01.
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  11. ^ a b Patrignani, C.; et al. (. See p. 768
  12. .
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  14. ^ "The BIPM and the evolution of the definition of the metre". Bureau International des Poids et Mesures. 2014-07-26. Retrieved 2016-06-23.
  15. ^ Penzes, William B. (2009-01-08). "Time Line for the Definition of the Meter". National Institute of Standards and Technology. Archived from the original on 2016-08-12. Retrieved 2016-06-23.
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  18. ^ Gibbs, Philip (1997). "How is the speed of light measured?". Department of Mathematics, University of California. Archived from the original on 2015-08-21. Retrieved 2007-03-19.
  19. ^ Unit of length (meter), NIST
  20. ^ "Spectra of Gas Discharges". Archived from the original on 2011-04-02. Retrieved 2009-10-04.
  21. ^ "Krypton" (PDF). Argonne National Laboratory, EVS. 2005. Archived from the original (PDF) on 2009-09-29. Retrieved 2007-03-17.
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    .
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  25. ^ Thonnard, Norbert; MeKay, Larry D.; Labotka, Theodore C. (2001-02-05). "Development of Laser-Based Resonance Ionization Techniques for 81-Kr and 85-Kr Measurements in the Geosciences" (PDF). University of Tennessee, Institute for Rare Isotope Measurements. pp. 4–7. Retrieved 2007-03-20.
  26. ^ "Resources on Isotopes". U.S. Geological Survey. Archived from the original on 2001-09-24. Retrieved 2007-03-20.
  27. ^ a b Bartlett, Neil (2003). "The Noble Gases". Chemical & Engineering News. Retrieved 2006-07-02.
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  34. ^ "Periodic Table of the Elements" (PDF). Los Alamos National Laboratory's Chemistry Division. pp. 100–101. Archived from the original (PDF) on November 25, 2006. Retrieved 2007-04-05.
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  37. ^ "How Products are Made: Krypton". Retrieved 2006-07-02.
  38. .
  39. ^ "Mercury in Lighting" (PDF). Cape Cod Cooperative Extension. Archived from the original (PDF) on 2007-09-29. Retrieved 2007-03-20.
  40. ^ Lighting: Full-Size Fluorescent Lamps. McGraw-Hill Companies, Inc. (2002)
  41. ^ Properties, Applications and Uses of the "Rare Gases" Neon, Krypton and Xenon. Uigi.com. Retrieved on 2015-11-30.
  42. ^ "Laser Devices, Laser Shows and Effect" (PDF). Archived from the original (PDF) on 2007-02-21. Retrieved 2007-04-05.
  43. ^ Sethian, J.; M. Friedman; M. Myers. "Krypton Fluoride Laser Development for Inertial Fusion Energy" (PDF). Plasma Physics Division, Naval Research Laboratory. pp. 1–8. Archived from the original (PDF) on 2011-09-29. Retrieved 2007-03-20.
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Further reading

External links