| Discovery date | 1898 |
| Discovered by | Sir William Ramsay and Morris Travers |
| Origin of the name | The name is derived from the Greek 'kryptos', meaning hidden. |
| Allotropes |
|
Kr
Krypton
36
83.798
| Group | 18 | Melting point | −157.37°C, −251.27°F, 115.78 K |
| Period | 4 | Boiling point | −153.415°C, −244.147°F, 119.735 K |
| Block | p | Density (g cm−3) | 0.003425 |
| Atomic number | 36 | Relative atomic mass | 83.798 |
| State at 20°C | Gas | Key isotopes | 84Kr |
| Electron configuration | [Ar] 3d104s24p6 | CAS number | 7439-90-9 |
| ChemSpider ID | 5223 | ChemSpider is a free chemical structure database | |
Image explanation
There are many different isotopes of krypton. This symbol represents the isotope krypton-86.
Appearance
Krypton is a gas with no colour or smell. It does not react with anything except fluorine gas.
Uses
Krypton is used commercially as a filling gas for energy-saving fluorescent lights. It is also used in some flash lamps used for high-speed photography.
Unlike the lighter gases in its group, it is reactive enough to form some chemical compounds. For example, krypton will react with fluorine to form krypton fluoride. Krypton fluoride is used in some lasers.
Radioactive krypton was used during the Cold War to estimate Soviet nuclear production. The gas is a product of all nuclear reactors, so the Russian share was found by subtracting the amount that came from Western reactors from the total in the air.
From 1960 to 1983 the isotope krypton-86 was used to define the standard measure of length. One metre was defined as exactly 1,650,763.73 wavelengths of a line in the atomic spectrum of the isotope.
Biological role
Krypton has no known biological role.
Natural abundance
Krypton is one of the rarest gases in the Earth’s atmosphere. It makes up just 1 part per million by volume. It is extracted by distillation of air that has been cooled until it is a liquid.
Having discovered the noble gas argon, extracted from air, William Ramsay and Morris William Travers of University College, London, were convinced this must be one of a new group of elements of the periodic table. They decided others were likely to be hidden in the argon and by a process of liquefaction and evaporation they hoped it might leave behind a heavier component, and it did. It yielded krypton in the afternoon of 30th May 1898, and they were able to isolate about 25 cm3 of the new gas. This they immediately tested in a spectrometer, and saw from its atomic spectrum that it was a new element.
| Atomic radius, non-bonded (Å) | 2.02 | Covalent radius (Å) | 1.16 |
| Electron affinity (kJ mol−1) | Not stable |
Electronegativity (Pauling scale) |
Unknown |
|
Ionisation energies (kJ mol−1) |
1st
1350.757
2nd
2350.367
3rd
3565.13
4th
5065.5
5th
6242.6
6th
7574.1
7th
10710
8th
12138.049
|
||
| Common oxidation states | 2 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 78Kr | 77.920 | 0.355 |
> 1.5 x 1021 y |
EC-EC |
|
| 80Kr | 79.916 | 2.286 | - | - | |
| 82Kr | 81.913 | 11.593 | - | - | |
| 83Kr | 82.914 | 11.5 | - | - | |
| 84Kr | 83.911 | 56.987 | - | - | |
| 86Kr | 85.911 | 17.279 | - | - | |
|
|
|
Specific heat capacity (J kg−1 K−1) |
248 | Young's modulus (GPa) | Unknown | |||||||||||
| Shear modulus (GPa) | Unknown | Bulk modulus (GPa) | Unknown | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
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| Pressure (Pa) |
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| Listen to Krypton Podcast |
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Transcript :
Chemistry in its element: krypton (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello, this week Superman makes an appearance and we're not talking about the rather tacky 1980s dance either, we're talking Krypton. Here's UCL's Angelos Michaelides. Angelos Michaelides Krypton is a fictional planet in the DC Comics universe, and the native world of the super-heroes Superman and, in some tellings, Supergirl, and Krypto the "super dog". Krypton has been portrayed consistently as having been destroyed just after Superman's flight from the planet, with exact details of its destruction varying by time period, writers and franchise. So much for trying to do a "wikipedia" search for this "hidden" element! The story of its discovery, however, reveals a Victorian man of Science who, in his own way, qualifies as a superhero. Born in Glasgow in 1852, William Ramsay was already established as one of the foremost chemists of his day when he took up his appointment at University College London in 1887. The chair to which he succeeded had been occupied by leaders of scientific progress and, almost immediately after entering on his new duties, he was elected as a Fellow of The Royal Society. Great things were therefore believed of him, but nobody could have foreseen the discoveries which came so rapidly. Ramsay's colleagues of this period describe him as "charming, witty, and generous" - traits which no doubt made him an easy man with whom to collaborate. Lord Rayleigh, himself an eminent physicist, was therefore lucky in more ways than one that Ramsay responded to his letter to Nature in September 1892. In it, Lord Rayleigh had expressed puzzlement as to why atmospheric nitrogen was of greater density than nitrogen derived from chemical sources, and wondered if any chemist would like to turn his mind to this anomaly. It does not appear that anyone except Professor Ramsay attempted to attack the question experimentally. Correspondence between the two men reveals the enthusiasm with which Ramsay set to the task and details painstaking and meticulous work first to isolate sufficient atmospheric nitrogen and then to test it, using fractional distillation, for impurities, - anything, basically, that wasn't nitrogen. In this way, Ramsay wrote to Rayleigh : "We may discover a new element". In fact, they discovered Argon, and Ramsay went on to discover an entirely new class of gases. In 1904, he was awarded the Nobel Prize for Chemistry for the discovery of argon, neon, xenon and, of course, krypton. Like its fellows, krypton is a colourless, odourless, tasteless, noble gas that occurs in trace amounts in the atmosphere. Like the other noble gases, it too is useful in lighting and photography, and its high light output in plasmas allows it to play an important role in many high-powered lasers. Unlike its lighter fellows it is reactive enough to form chemical compounds: krypton fluoride being the main example, which has led to the development of the krypton flouride laser. A laser of invisible light developed in the 1980's by the Los Alamos National Laboratory, which has found uses in fusion research and lithography. The heaviest stable krypton isotope, krypton 86, rose to prominence in the second half of the last century with a tad over one and a half million wavelengths of its orange-red spectral line being used as the official distance of a metre. But the potential applications and practical uses of krypton are perhaps irrelevant in the story of its discovery. The point of Ramsay's work was not to put his knowledge to some utilitarian purpose - the point was to discover. Scientific endeavour is perhaps too often judged by whether or not its results are "useful". But discovery and knowledge are sometimes an end in themselves. The purist knows the joy of discovering that which was hitherto unknown. Sir William Ramsay was a purist - a man with an insatiable appetite to better understand the world. He travelled to Canada, the United States, Finland, India, and Turkey with his wife, Lady Ramsay. He was a man open to new ideas, always endeavouring on his travels to learn local languages and customs and always alive to new experiences. One anecdote, related by a travelling companion to Iceland, describes him standing on the site of a geyser with a small glass jar, capturing gases as they erupt from underfoot. The image is unmistakably one of a childlike fascination with nature, in a man whose dedication to research knew no limits. In his 1918 biography of Ramsay, Sir William Tilden describes him as a man "ever filled with that divine curiosity which impels the discoverer forward" who enjoyed the satisfaction of knowing that he was achieving something. Indeed, in a memorial lecture, for his late friend Henri Moissan in 1912, Ramsay quoted the following words: "But what I cannot convey in the following pages is the keen pleasure I have experienced in the pursuit of these discoveries. To plough a new furrow; to have full scope to follow my own inclination; to see on all sides new subjects of study bursting upon me, that awakens a true joy which only those can experience who have themselves tasted the delights of research" What's left, then, is the joy of finding what is hidden, a fact reflected in the very name of this element, Krypton, taken from "krypto", Greek for hidden. And nothing to do with a SuperDog. Chris Smith The hidden element that Lord Raleigh suspected might be there and William Ramsay actually uncovered. Thank you very much to Angelos Michaelides. He's based at University College London. Next week to one of those elements, the chemical symbol of which appears to bear absolutely no relationship to the name of the substance itself. Why? Katherine Holt Many centuries ago mid-European tin smelters observed that when a certain mineral was present in the tin ore, their yield of tin was much reduced. They called this mineral 'wolfs foam' because, they said, it devoured the tin much like a wolf would devour a sheep! Chris Smith And Katherine Holt will be telling us the tale behind tungsten's letter W on the periodic table in next week's Chemistry in its Element, hope you can join us. I'm Chris Smith, thank you for listening and goodbye. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements. (End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Derived in part from material provided by the British Geological Survey © NERC.
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Produced by The Naked Scientists.
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
© Murray Robertson 1998-2017.
Data
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
Uses and properties
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Supply risk data
Derived in part from material provided by the British Geological Survey © NERC.
History text
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Podcasts
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
