Periodic Table > Krypton
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses/Interesting Facts below.

 

Fact Box Terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact Box

 
Group 18  Melting point -157.36 oC, -251.248 oF, 115.79 K 
Period Boiling point -153.415 oC, -244.147 oF, 119.735 K 
Block Density (kg m-3) 3000 (85 K) 
Atomic number 36  Relative atomic mass 83.798  
State at room temperature Gas  Key isotopes 84Kr 
Electron configuration [Ar] 3d104s24p6  CAS number 7439-90-9 
ChemSpider ID 5223 ChemSpider is a free chemical structure database
 

Interesting Facts terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses / Interesting Facts

 
Image explanation
The symbol represents the isotope Krypton 86 and the gaseous nature of the element.
Appearance
A colourless, odourless gas that is inert to everything but fluorine gas.
Source

Uses

Krypton is used commercially as a low-pressure filling gas for fluorescent lights. It is also used in certain photographic flash lamps for high-speed photography. Unlike the lighter inert gases 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. Radioactive krypton was used 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 comes from Western reactors from the total in the air. The isotope krypton-86 has a line in its atomic spectrum that became, from 1960 to 1983, the standard measure of length: 1 metre was defined as exactly 1,650,763.73 wavelengths of this line.

Biological role
Krypton has no known biological role.
Natural abundance
Krypton is obtained by distillation from liquid air despite being one of the rarest gases in the Earth’s atmosphere, accounting for only 1 part per million by volume.
 
Atomic Data Terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic Data

 
Atomic radius, non-bonded (Å) 2.020 Covalent radius (Å) 1.16
Electron affinity (kJ mol-1) Not stable Electronegativity
(Pauling scale)
Unknown
Ionisation energies
(kJ mol-1)
 
1st
1350.756
2nd
2350.365
3rd
3565.130
4th
5065.476
5th
6242.596
6th
7574.093
7th
10709.864
8th
12138.038
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply Risk

 
Scarcity factor Unknown
Country with largest reserve base Unknown
Crustal abundance (ppm) Unknown
Leading producer Unknown
Reserve base distribution (%) Unknown
Production concentration (%) Unknown
Total governance factor(production) Unknown
Top 3 countries (mined)
  • Unknown
Top 3 countries (production)
  • Unknown
 

Oxidation states/ Isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation States / Isotopes

 
Common oxidation states 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  78Kr 77.92 0.355
  80Kr 79.916 2.286 > 1.5 x 1021 EC-EC 
  82Kr 81.913 11.593
  83Kr 82.914 11.5
  84Kr 83.912 56.987
  86Kr 85.911 17.279
 

Pressure and Temperature - Advanced Terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure / Temperature - Advanced

 
Molar heat capacity
(J mol-1 K-1)
20.786 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
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History

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.

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Podcasts

Listen to Krypton Podcast
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 elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

(End promo)

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Resources

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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.