| Atomic Mass | 83.798 |
|---|---|
| Electron Configuration | [Ar]4s23d104p6 |
| Oxidation States | 0 |
| Year Discovered | 1898 |
| Atomic Mass | 83.798 |
|---|---|
| Electron Configuration | [Ar]4s23d104p6 |
| Oxidation States | 0 |
| Year Discovered | 1898 |
| Element Name | Krypton |
|---|---|
| Element Symbol | Kr |
| InChI | InChI=1S/Kr |
| InChIKey | DNNSSWSSYDEUBZ-UHFFFAOYSA-N |
| Atomic Weight |
83.798(2) 83.798 83.79 83.798(2) |
|---|---|
| Electron Configuration |
[Ar]4s23d104p6 |
| Atomic Radius |
Van der Waals Atomic Radius : 202 pm (Van der Waals) Covalent Atomic Radius : 116(4) pm (Covalent) |
| Oxidation States |
2, 1, 0 (rarely more than 0; unknown oxide) |
| Ground Level |
1S0 |
| Ionization Energy |
14.000 eV 13.9996055 ± 0.0000020 eV |
| Electronegativity |
Pauling Scale Electronegativity : 3(Pauling Scale) Allen Scale Electronegativity : 2.966(Allen Scale) |
| Electron Affinity |
0eV -0.42eV |
| Atomic Spectra |
Lines Holdings Levels Holdings |
| Physical Description |
Gas |
| Element Classification |
Non-metal |
| Element Period Number |
4 |
| Element Group Number |
18 - Noble Gas |
| Density |
0.003733 grams per cubic centimeter |
| Melting Point |
115.79 K (-157.36°C or -251.25°F) -157.37°C |
| Boiling Point |
119.93 K (-153.22°C or -243.80°F) 153.415°C |
| Estimated Crustal Abundance |
1×10-4 milligrams per kilogram |
| Estimated Oceanic Abundance |
2.1×10-4 milligrams per liter |
The name derives from the Greek kryptos for "concealed" or "hidden". It was discovered in liquefied atmospheric air by the Scottish chemist William Ramsay and the English chemist Morris William Travers in 1898. A wavelength in the atomic spectrum of 86Kr is a fundamental standard of length.
Krypton was discovered on May 30, 1898 by Sir William Ramsay, a Scottish chemist, and Morris M. Travers, an English chemist, while studying liquefied air. Small amounts of liquid krypton remained behind after the more volatile components of liquid air had boiled away. The earth's atmosphere is about 0.0001% krypton.
From the Greek word kryptos, hidden. Discovered in 1898 by Ramsay and Travers in the residue left after liquid air had nearly boiled away. 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 86Kr. 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.
| Year | Atomic Weight (uncertainty) [u] | Reference |
|---|---|---|
| 2001 | 83.798(2) | https://doi.org/10.1351/pac200375081107 |
| 1969 | 83.80(1) | https://doi.org/10.1351/pac197021010091 |
| 1951 | 83.80 | https://doi.org/10.1039/JR9530000001 |
| 1932 | 83.7 | https://doi.org/10.1021/ja01343a001 |
| 1925 | 82.9 | https://doi.org/10.1039/CT9252700913 |
| 1911 | 82.92 | https://doi.org/10.1021/ja01928a001 |
| 1910 | 83.0 | https://doi.org/10.1021/ja01919a001 |
| 1902 | 81.8 | https://doi.org/10.1007/BF01370337 |
Krypton is a "noble" gas. It is characterized by its brilliant green and orange spectral lines.
The high cost of obtaining krypton from the air has limited its practical applications. Krypton is used in some types of photographic flashes used in high speed photography. Some 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 greenish-yellow light. In 1960, the length of the meter was defined in terms of the orange-red spectral line of krypton-86, an isotope of krypton.
Once thought to be completely inert, krypton is known to form a few compounds. Krypton difluoride (KrF2) is the easiest krypton compound to make and gram amounts of it have been produced.
For those that are curious, pictures of krypton gas and krypton plasma can be found in the Questions and Answers section of this site.
Krypton clathrates are prepared using hydroquinone and phenol. 85Kr can be used for chemical analysis by imbedding the isotope in various solids. During this process, kryptonates are formed. Kryptonate activity is sensitive to chemical reactions at the solution surface. Estimates of the concentration of reactants are therefore made possible. Krypton is used in certain photographic flash lamps for high-speed photography.
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. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases."
See more information at the Krypton compound page.
| CID | Name | Formula | SMILES | Molecular Weight |
|---|---|---|---|---|
| 5416 | krypton | Kr | [Kr] | 83.80 |
| 66380 | krypton-81 | Kr | [81Kr] | 80.91659 |
| 104816 | krypton-85 | Kr | [85Kr] | 84.91253 |
| 71309537 | krypton-84 | Kr | [84Kr] | 83.91149773 |
| 71309538 | krypton-86 | Kr | [86Kr] | 85.91061062 |
| 71309637 | krypton-80 | Kr | [80Kr] | 79.916378 |
| 177606 | krypton-79 | Kr | [79Kr] | 78.92008 |
| 177736 | krypton-89 | Kr | [89Kr] | 88.91784 |
| 25087179 | krypton-87 | Kr | [87Kr] | 86.913355 |
| 25087184 | krypton-88 | Kr | [88Kr] | 87.91445 |
| 71309636 | krypton-78 | Kr | [78Kr] | 77.920366 |
| 71309638 | krypton-82 | Kr | [82Kr] | 81.91348115 |
| 11996921 | krypton-77 | Kr | [77Kr] | 76.92467 |
| 44154744 | krypton-76 | Kr | [76Kr] | 75.92591 |
| 71309103 | krypton-83 | Kr | [83Kr] | 82.91412652 |
| Stable Isotope Count | 5 |
|---|---|
| Summary | Naturally occurring krypton contains six stable isotopes. Seventeen other unstable isotopes are recognized. The spectral lines of krypton are easily produced and some are very sharp. 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 can exist. 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+. |
85Kr (with a half-life of 10.7 years) has been used in atmospheric monitoring programs to track the effect of atomic facilities on the surrounding environment. 85Kr is co-generated with plutonium in the fuel elements of nuclear fission reactors and can be monitored at short distances (i.e. 1 to 5 km) from an area of clandestine plutonium separation from spent fuel from the nuclear reactor. The differences in 85Kr levels in the atmosphere have been used to estimate the amount of plutonium separated at weekly intervals. The production of plutonium for nuclear weapons and the output from commercial reprocessing plants have released large amounts of 85Kr into the atmosphere [283].
85Kr has minimal natural production in the Earth, but its concentration in the atmosphere has increased steadily because of human activities related to the nuclear industry. 85Kr enters oceans, lakes, and groundwater through equilibration of the water with air. 85Kr is produced terrestrially as a fission product of nuclear reactors and released into the atmosphere with the noble gases. It is also produced in the atmosphere via the cosmic ray neutron-activation reaction, 84Kr (n, γ) 85Kr. Thus, the 85Kr specific activity can be used to determine the time since water was isolated from the atmosphere (Fig. IUPAC.36.1). This approach provides a valuable addition to the use of tritium (3H) as an indicator of ocean circulation and groundwater age on decadal (a period of 10 consecutive years) time scales [284], [285].
Krypton stable isotopes react in the upper atmosphere by cosmic-ray-induced spallation and neutron activation to produce radioactive 81Kr, with a half-life of approximately 2.1×105 years. In the atmosphere, 81Kr is chemically inert and has a long residence time; because of these characteristics, it is expected that 81Kr has a relatively constant and well-constrained atmospheric source. Natural cosmogenic 81Kr is incorporated from air into infiltrating groundwater and has been used to determine the age of groundwater over time scales ranging to over 106 years [286], [287], [288], [289].
![Fig. IUPAC.36.1: ⁸¹Kr has been used to date the groundwater being discharged from springs and wells. The photo shows collection of a ⁸¹Kr sample from an artesian well in Farafra Oasis, Egypt [289]. (Photo Source: N. C. Sturchio, University of Delaware, Delaware, USA).](https://pubchem.ncbi.nlm.nih.gov/images/iupac/j_pac-2015-0703_fig_055.jpg)
85Kr has been used as the illumination element of indicator lights of appliances and can be combined with phosphors to create materials that glow in the dark. Light is created when radiation from 85Kr strikes the phosphor [98]. 85Kr can be used to detect container leaks by placing the radioactive gas inside a container and measuring (with a radiation detecting device) the amount of radioactive 85Kr that escapes. Because the gas is inert, Kr will not react with anything else in the container [98].
A patient can inhale gaseous radioactive 85Kr, which is then absorbed in the bloodstream, enabling the blood flow of the patient to be studied. Movement of the 85Kr can be tracked with a radiation detector to reveal pathways followed by the blood and to quantify blood velocity [99], [284], [290].
| Isotope | Atomic Mass (uncertainty) [u] | Abundance (uncertainty) | |
|---|---|---|---|
| 78Kr | 77.920 366(2) | 0.003 55(3) | 0.00355(3) |
| 80Kr | 79.916 378(5) | 0.022 86(10) | 0.02286(10) |
| 82Kr | 81.913 481 15(4) | 0.115 93(31) | 0.11593(31) |
| 83Kr | 82.914 126 52(6) | 0.115 00(19) | 0.11500(19) |
| 84Kr | 83.911 497 73(3) | 0.569 87(15) | 0.56987(15) |
| 86Kr | 85.910 610 63(3) | 0.172 79(41) | 0.17279(41) |
| Nuclide | Atomic Mass and Uncertainty [u] | Half Life and Uncertainty | Discovery Year | Decay Modes, Intensities and Uncertainties [%] |
|---|---|---|---|---|
| 67Kr | 66.983305 ± 0.000455 [Estimated] | 7.4 ms ± 2.9 | 2016 | 2p=37±1.4%; β+ ? |
| 68Kr | 67.972489 ± 0.000537 [Estimated] | 21.6 ms ± 3.3 | 2016 | β+= ?; β+p=90±1.1%; p ? |
| 69Kr | 68.965496 ± 0.000322 [Estimated] | 27.9 ms ± 0.8 | 1995 | β+=100%; β+p=94±0.5% |
| 70Kr | 69.955877 ± 0.000215 [Estimated] | 45.00 ms ± 0.14 | 1995 | β+=100%; β+p<1.3% |
| 71Kr | 70.950265695 ± 0.000138238 | 98.8 ms ± 0.3 | 1981 | β+=100%; β+p=2.1±0.7% |
| 72Kr | 71.942092406 ± 0.0000086 | 17.16 s ± 0.18 | 1973 | β+=100% |
| 73Kr | 72.939289193 ± 0.000007061 | 27.3 s ± 1.0 | 1972 | β+=100%; β+p=0.25±0.3% |
| 73Krm | 72.939289193 ± 0.000007061 | 107 ns ± 10 | 1993 | IT=100% |
| 74Kr | 73.933084016 ± 0.000002161 | 11.50 m ± 0.11 | 1960 | β+=100% |
| 75Kr | 74.930945744 ± 0.0000087 | 4.60 m ± 0.07 | 1960 | β+=100% |
| 76Kr | 75.925910743 ± 0.000004308 | 14.8 h ± 0.1 | 1954 | β+=100% |
| 77Kr | 76.924669999 ± 0.0000021 | 72.6 m ± 0.9 | 1948 | β+=100% |
| 77Krm | 76.924669999 ± 0.0000021 | 118 ns ± 12 | 1975 | IT=100% |
| 78Kr | 77.920366341 ± 0.000000329 | Stable >110Ey | 1920 | IS=0.355±0.3%; 2β+ ? |
| 79Kr | 78.920082919 ± 0.000003736 | 35.04 h ± 0.10 | 1948 | β+=100% |
| 79Krm | 78.920082919 ± 0.000003736 | 50 s ± 3 | 1940 | IT=100% |
| 80Kr | 79.916377940 ± 0.000000745 | Stable | 1920 | IS=2.286±1% |
| 81Kr | 80.916589703 ± 0.000001152 | 229 ky ± 11 | 1950 | ε=100% |
| 81Krm | 80.916589703 ± 0.000001152 | 13.10 s ± 0.03 | 1940 | IT≈100%; ε=0.0025±0.4% |
| 82Kr | 81.91348115368 ± 0.00000000591 | Stable | 1920 | IS=11.593±3.1% |
| 83Kr | 82.914126516 ± 0.000000009 | Stable | 1920 | IS=11.500±1.9% |
| 83Krm | 82.914126516 ± 0.000000009 | 156.8 ns ± 0.5 | 1963 | IT=100% |
| 83Krn | 82.914126516 ± 0.000000009 | 1.830 h ± 0.013 | 1971 | IT=100% |
| 84Kr | 83.91149772708 ± 0.0000000041 | Stable | 1920 | IS=56.987±1.5% |
| 84Krm | 83.91149772708 ± 0.0000000041 | 1.83 us ± 0.04 | 1982 | IT=100% |
| 85Kr | 84.912527260 ± 0.000002147 | 10.728 y ± 0.007 | 1940 | β-=100% |
| 85Krm | 84.912527260 ± 0.000002147 | 4.480 h ± 0.008 | 1937 | β-=78.8±0.5%; IT=21.2±0.5% |
| 85Krn | 84.912527260 ± 0.000002147 | 1.82 us ± 0.05 | 1989 | IT=100% |
| 86Kr | 85.91061062468 ± 0.00000000399 | Stable | 1920 | IS=17.279±4.1%; 2β- ? |
| 87Kr | 86.913354759 ± 0.000000264 | 76.3 m ± 0.5 | 1940 | β-=100% |
| 88Kr | 87.914447879 ± 0.0000028 | 2.825 h ± 0.019 | 1939 | β-=100% |
| 89Kr | 88.917835449 ± 0.0000023 | 3.15 m ± 0.04 | 1940 | β-=100% |
| 90Kr | 89.919527929 ± 0.000002 | 32.32 s ± 0.09 | 1951 | β-=100% |
| 91Kr | 90.923806309 ± 0.0000024 | 8.57 s ± 0.04 | 1951 | β-=100%; β-n ? |
| 92Kr | 91.926173092 ± 0.0000029 | 1.840 s ± 0.008 | 1951 | β-=100%; β-n=0.0332±2.5% |
| 93Kr | 92.931147172 ± 0.0000027 | 1.287 s ± 0.010 | 1951 | β-=100%; β-n=1.95±1.1% |
| 94Kr | 93.934140452 ± 0.000013 | 212 ms ± 4 | 1972 | β-=100%; β-n=1.11±0.7% |
| 95Kr | 94.939710922 ± 0.00002 | 114 ms ± 3 | 1994 | β-=100%; β-n=2.87±1.8%; β-2n ? |
| 95Krm | 94.939710922 ± 0.00002 | 1.582 us ± 0.022 | 2006 | IT=100% |
| 96Kr | 95.943014473 ± 0.000020695 | 80 ms ± 8 | 1994 | β-=100%; β-n=3.7±0.4% |
| 97Kr | 96.949088782 ± 0.00014 | 62.2 ms ± 3.2 | 1997 | β-=100%; β-n=6.7±0.6%; β-2n ? |
| 98Kr | 97.952635 ± 0.000322 [Estimated] | 42.8 ms ± 3.6 | 1997 | β-=100%; β-n=7.0±1%; β-2n ? |
| 99Kr | 98.958776 ± 0.000429 [Estimated] | 40 ms ± 11 | 1997 | β-=100%; β-n=11±0.7%; β-2n ? |
| 100Kr | 99.962995 ± 0.000429 [Estimated] | 12 ms ± 8 | 1997 | β-=100%; β-n ?; β-2n ? |
| 101Kr | 100.969318 ± 0.000537 [Estimated] | 9 ms >400ns [Estimated] | 2010 | β- ?; β-n ?; β-2n ? |
