Krypton (Kr)

Krypton is a chemical element with the atomic number 36 in the periodic table. According to the chemical calculations, there is about 0.000108 to 0.000114 percent of krypton gas in Earth’s atmosphere. Trace amounts of krypton can also be naturally formed in some minerals contained in Earth’s crust by the disintegration of radioactive elements such as uranium. 

Being a member of the noble gases family of elements, krypton has eight valence electrons which make it a chemically inert gas with limited everyday use. Its most popular commercial application is as a filling gas for energy-saving fluorescent lights.

Fact Box

Chemical and Physical Properties of Krypton

The symbol in the periodic table of elements: Kr

Atomic number: 36

Atomic weight (mass): 83.80 g.mol-1

Group number: 18

Period: 4 (p-block)

Color: Colorless

Physical state: Gas at room temperature

Half-life: From 32(10) milliseconds to 9.2 (+5.5−2.6) ± 1.3×1021 years

Electronegativity according to Pauling: 3.00

Density: 3.73 10-3 at 20°C

Melting point: −157.37°C, −251.27°F, 115.78 K

Boiling point: −153.415°C, −244.147°F, 119.735 K

Van der Waals radius: 0.197 nm

Ionic radius: Unknown

Isotopes: 434

Most characteristic isotope: 84Kr

Electronic shell: [Ar] 3d104s24p6

The energy of the first ionization: 1351 kJ.mol-1

The energy of the second ionization: 2350.4 kJ.mol-1

The energy of the third ionization: 3565 kJ.mol-1

Discovery date: In 1898 by Sir William Ramsay and Morris Travers 

With the periodic table symbol Kr, atomic number 36, atomic mass of 83.80 g.mol-1, and electron configuration [Ar] 3d104s24p6, krypton is a colorless, odorless, and tasteless inert gas with a cubic face-centered atomic structure. It reaches its boiling point at −153.415°C, −244.147°F, 119.735 K, while the melting point is achieved at −157.37°C, −251.27°F, 115.78 K. This member of the noble gases group has an atomic radius according to van der Waals is 0.197 nm, while on the Pauling’s scale of electronegativity krypton has a value of 3.00. 

Krypton is not a chemically reactive element. The only chemical it reacts with is fluorine gas. Element 36 has two allotropes: krypton gas (occurring in the atmosphere of the Earth) and solid kryptonite (occurring in minuscule amounts in some minerals found in Earth’s crust). At normal temperature and pressure conditions, krypton is 2.8 times as dense as air. Its most characteristic physical properties are the brilliant green and orange spectral lines which appear very sharp.             

How Was Krypton Discovered?

This chemical element was discovered by two British chemists in London, 1898. In search of the predicted chemical element that would fit between helium and argon, the Scottish chemist William Ramsay and his English assistant Morris Travers succeeded in discovering an entire family of elements in the residue of a completely evaporated sample of liquid air – the noble gasses family. 

Namely, after these discoverers managed to extract the noble gas argon from the air, they were convinced that there must be a completely new group of elements. This further triggered the scientific curiosity of Sir Ramsay and Travers, so they attempted to discover the other members of the noble gas group contained in the air by using the methods of liquefaction and evaporation. 

On May 30th, 1898, these dedicated chemists had a reason to be proud of their work. On this date in history, they had managed to isolate 25 cm3 of the new gas for the first time. By conducting a spectrometry test, Ramsay and Tennant observed several very sharp and intense green and yellow lines in the spectrum, which served as firm evidence for the discovery of the new element 36 – krypton (Kr).

How Did Krypton Get Its Name?

The name of this chemical element originates from the Greek word ‘kryptos‘, which means ‘hidden’. This refers to the fact that krypton was discovered as an impurity ‘hidden’ in the residue of atmospheric nitrogen distillate. 

Where Can You Find Krypton?

Krypton is one of the rarest gases that have been traced in Earth’s atmosphere, but its presence in the Universe is abundant, especially in meteorites. According to the chemical calculations, there is 1/10th of the milliliter of Krypton for every 100 liters of air in our planet’s atmosphere. 

At sea level, dry air contains 78.08% nitrogen and 20.95% oxygen, as well as 0.93% argon, 0.0018% neon, 0.00052% helium, 0.00011% krypton, and 0.0000087% xenon. Dry air also is made up of carbon dioxide, hydrogen, methane, nitric oxide, and ozone. 

Commercially, krypton is obtained from uranium fission in nuclear plants, and by fractional distillation – the same method used for its discovery.  

Krypton in Everyday Life

Element 36 is not a typical everyday substance we see implemented in the items we frequently use. However, few instances depict the practical use of krypton in our everyday life:

  • Similar to the other noble gases, krypton is also used in lighting and photography;
  • The radioactive krypton-81 isotope is applied in the dating of underground waters. Its reaction becomes highly volatile near the surface;
  • In order to slow down the neutron fission of uranium, a mixture of both unstable and stable isotopes of krypton is used;
  • The most stable isotope of this chemical element, krypton-85, is applied in a light source to excite phosphors;
  • Krypton-83 isotope is applied in MRI (magnetic resonance imaging). With the help of this isotope, hydrophilic and hydrophobic surfaces that are contained in an airway can be differentiated;
  • When used with argon in fluorescent lights, krypton supports improvement their brightness;
  • Mixed with nitrogen, krypton extends the lifetime of incandescent lights;
  • Commercially, this noble gas is often used as a filling gas for energy-saving fluorescent lights. 

How Dangerous Is Krypton?

Being a minimally toxic inert gas, krypton is classified as a simple asphyxiant. The presence of large quantities of this rare atmospheric gas in a closed space may lead to oxygen depletion which is exceptionally dangerous. 

Inhalation of excessive amounts of krypton triggers adverse health effects, such as:

  • Dizziness;
  • Nausea;
  • Vomiting.

Some of the symptoms of krypton exposure that may lead to death include:

  • Loss of consciousness;
  • Errors in judgment;
  • Confusion.

Environmental Effects of Krypton

Being a non-toxic and chemically inert substance, krypton is not considered a hazardous substance upon the geological, biological, or aquatic systems of our environment. 

Isotopes of Krypton

This chemical element has 34 isotopes, with atomic masses ranging from 69Kr to 102Kr. Naturally occurring krypton consists of five stable isotopes and radioisotopes: 78Kr, 80Kr, 82Kr, 83Kr, 84Kr, and 86Kr. 

Krypton-81 is referred to as a cosmogenic nuclide because it is produced by the irradiation of krypton-80 due to interaction with cosmic rays. It has a half-life of 230,000 years. Also, krypton-85 is produced by uranium and plutonium fission. This form of krypton is typically released during the dissolution of spent fuel rods in the nuclear-reprocessing facilities.

Nuclide [n 1]ZNIsotopic mass (Da) [n 2][n 3]Half-life [n 4][n 5]Decay mode [n 6]Daughter isotope [n 7][n 8]Spin and parity [n 9][n 5]Natural abundance (mole fraction)
Excitation energyNormal proportionRange of variation
69Kr363368.96518(43)#32(10) msβ+69Br5/2−#
70Kr363469.95526(41)#52(17) msβ+70Br0+
71Kr363570.94963(70)100(3) msβ+ (94.8%)71Br(5/2)−
β+, p (5.2%)70Se
72Kr363671.942092(9)17.16(18) sβ+72Br0+
73Kr363772.939289(7)28.6(6) sβ+ (99.32%)73Br3/2−
β+, p (.68%)72Se
74Kr363873.9330844(22)11.50(11) minβ+74Br0+
75Kr363974.930946(9)4.29(17) minβ+75Br5/2+
76Kr364075.925910(4)14.8(1) hβ+76Br0+
77Kr364176.9246700(21)74.4(6) minβ+77Br5/2+
78Kr[n 10]364277.9203648(12)9.2 +5.5 −2.6 ±1.3×1021 y[1]Double EC78Se0+0.00355(3)
79Kr364378.920082(4)35.04(10) hβ+79Br1/2−
81Kr[n 11]364580.9165920(21)2.29(11)×105 yEC81Br7/2+trace
83Kr[n 12]364782.914136(3)Stable9/2+0.11500(19)
84Kr[n 12]364883.911507(3)Stable0+0.56987(15)
85Kr[n 12]364984.9125273(21)10.776(3) yβ−85Rb9/2+trace
86Kr[n 13][n 12]365085.91061073(11)Observationally Stable[n 14]0+0.17279(41)
87Kr365186.91335486(29)76.3(5) minβ−87Rb5/2+
88Kr365287.914447(14)2.84(3) hβ−88Rb0+
89Kr365388.91763(6)3.15(4) minβ−89Rb3/2(+#)
90Kr365489.919517(20)32.32(9) sβ−90mRb0+
91Kr365590.92345(6)8.57(4) sβ−91Rb5/2(+)
92Kr365691.926156(13)1.840(8) sβ− (99.96%)92Rb0+
β−, n (.033%)91Rb
93Kr365792.93127(11)1.286(10) sβ− (98.05%)93Rb1/2+
β−, n (1.95%)92Rb
94Kr365893.93436(32)#210(4) msβ− (94.3%)94Rb0+
β−, n (5.7%)93Rb
95Kr365994.93984(43)#114(3) msβ−95Rb1/2(+)
96Kr366095.942998(62)[5]80(7) msβ−96Rb0+
97Kr366196.94856(54)#63(4) msβ−97Rb3/2+#
β−, n96Rb
98Kr366297.95191(64)#46(8) ms0+
99Kr366398.95760(64)#40(11) ms(3/2+)#
100Kr366499.96114(54)#10# ms [>300 ns]0+
101Kr3665unknown>635 nsβ−, 2n99Rbunknown
β−, n100Rb

Source: Wikipedia

List of Krypton Compounds 

Krypton is a chemically inert substance. It adopts the oxidation states of +2 and 0 and forms a few chemical compounds. The list of krypton compounds contains the following items: 

  • Krypton fluoride
  • Krypton tetrachloride
  • Krypton difluoride
  • Krypton hexabromine
  • Krypton dichromate
  • Krypton chromate
  • Krypton tetrafluoride
  • Krypton dioxide

5 Interesting Facts and Explanations

  1. Krypton-86 is used as a reference for the standard measure of length. In 1960, the General Conference on Weight and Measurement defined the meter as “the length equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the p-d transitions between the levels of the krypton-86 atom”.
  2. Before discovering krypton, Sir William Ramsay succeeded in discovering elements helium, xenon, and argon. In 1904, Sir William Ramsay won the Nobel prize in chemistry for his contributions to the discovery of the inert gaseous elements in the air and also revealed the noble gases family of the periodic table. Sir Ramsey was also one of the first scientists who wrote textbooks based on the periodic classification of elements.
  3. The same year, this Scottish chemist and discoverer also shared the Nobel Prize in Physics with the British scientists John William Strutt, 3rd Baron Rayleigh, for their discovery of argon. 
  4. Until 1962, noble gases were considered completely chemically inert. By producing the first noble-gas compound (Xe+[PtF6]−, i.e. xenon hexafluoroplatinate), the British chemist Neil Bartlett managed to prove the contrary to some extent. 
  5. Element 36 is a chemical that has inspired both writers and movie-makers to create some notable images that are a part of our pop culture. And – it’s all in the name! In the American comic books published by DC Comics, the fictional planet Krypton is home to the most famous comic book and movie character Superman. Even the imaginary substance that takes away Superman’s powers, the green glowing (read: radioactive) kryptonite, has nothing to do with the real properties of element 36. 

Chemical Property and physical properties of element Krypton

Symbol of Krypton:Kr
Atomic Number of Krypton:36
Group of Krypton:Noble Gas
Crystal Structure of Krypton:Cubic: Face centered
Atomic Weight of Krypton:83.8
Shells of Krypton:2,8,18,8
Orbitals of Krypton:[Ar] 3d10 4s2 4p6
Valence of Krypton:0
Melting Point of Krypton:
Boiling Point of Krypton:
Electro Negativity of Krypton:0
Covalent Radius of Krypton:1.12 Å
Ionic Radius of Krypton:
Atomic Radius of Krypton:1.03 Å
Atomic Volume of Krypton:38.9 cm³/mol
Name Origin of Krypton:Greek: kryptos (hidden).
Discovered of Krypton By:Sir William Ramsey, M.W. Travers
Location:Great Britain
Pronounced of Krypton:KRIP-ton
Oxydation States of Krypton:0
Density of Krypton:0.003708 g/cm³
Uses of Krypton:Used in lighting products. Some is used as inert filler-gas in incandescent bulbs. Some is mixed with argon in fluorescent lamps. The most important use is in flashing stroboscopic lamps that outline airport runways.
Description of Krypton:Soft, silvery-white, highly reactive metal.