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About Krypton

Krypton Bohr

Krypton, atomic number 36, is one of the noble gases and is found in trace amounts (1 ppm) of the Earth’s atmosphere. The high cost of fractional distillation of liquefied air to isolate this element precludes widespread use in practical applications. When isolated, krypton is commercially used for high-speed photographic flash bulbs; and when mixed with other gases such as argon, is often present in fluorescent lamps. Krypton is mostly inert and few compounds containing krypton are known to exist. Krypton diflouride (KrF2) is one such compound – a volatile and colorless solid that can typically only be produced in amounts measured in grams.

When krypton is combined with fluorine, a host of industrial and scientific applications are made possible. Krypton fluoride lasers produce a deep-ultraviolet beam that is widely used in photolithography during the manufacturing process of semiconductor integrated circuits. Due to the short wavelength of its emitted light (λ = 248 nm), this type of laser is credited with significantly reducing piece-part spacing in microelectronic chips throughout the 1990s and 2000s. This increased the density of piece-parts on a microchip, transistors in a CPU for example, thereby increasing switching speed and lowering cost of manufacturing electronic devices. For these reasons, the krypton fluoride laser has been credited as one of the key contributors in maintaining Moore’s Law during this time frame.

Sir William Ramsay, chemist and recipient of the 1904 Nobel Prize in Chemistry for his isolation of noble gases, along with Morris Travers, discovered krypton in 1898 by evaporating components of liquefied air. Six naturally occurring, stable isotopes of krypton have been discovered since. One such isotope, 81Kr, has been found useful in dating groundwater. 85Kr is a byproduct of uranium or plutonium fission and is itself radioactive with a half-life of 10.76 years. 86Kr, with the 605nm wavelength characteristic of its orange-red spectral line, was declared the official internationally-accepted definition of ‘meter’ as a unit of measure in 1960; replacing a metal bar, before being replaced itself in 1983 by the distance that light travels in a vacuum.

Krypton Properties

Krypton Bohr ModelKrypton is a Block P, Group 18, Period 4 element. The number of electrons in each of Krypton's shells is 2, 8, 18, 8 and its electronic configuration is [Ar] 3d10 4s2 4p6. In its elemental form krypton's CAS number is 7439-90-9. The krypton atom has a covalent radius of 116± and it's Van der Waals radius is Krypton has a concentration about 1 ppm in the atmosphere and can be extracted from liquid air. Krypton was discovered and first isolated by Sir William Ramsay and Morris W. Travers in 1898. The origin of the name Krypton comes from the Greek word kryptos meaning "hidden".

Krypton information, including technical data, properties, and other useful facts are specified below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity, and thermal properties are included.

Symbol: Kr
Atomic Number: 36
Atomic Weight: 83.79
Element Category: noble gases
Group, Period, Block: 18, 4, p
Color: colorless
Other Names: Cripto
Melting Point: -157.36°C, -251.248°F, 115.79 K
Boiling Point: -153.415°C, -244.147°F, 119.735 K
Density: 3000 (85 K) kg·m3
Liquid Density @ Melting Point: 2.413 g·cm3
Density @ 20°C: 0.003708 g/cm3
Density of Solid: 2155 kg·m3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: 115.775 K, 73.53 kPa
Critical Point: 209.48 K, 5.525 MPa
Heat of Fusion (kJ·mol-1): 1.64
Heat of Vaporization (kJ·mol-1): 9.05
Heat of Atomization (kJ·mol-1): 0
Thermal Conductivity: 9.43×10-3  W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: 5R/2 = 20.786 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (gas, 23 °C) 220, (liquid) 1120 m·s-1
Pauling Electronegativity: 3
Sanderson Electronegativity: 2.91
Allred Rochow Electronegativity: 2.94
Mulliken-Jaffe Electronegativity: 3.00 (12.5% s orbital)
Allen Electronegativity: 2.966
Pauling Electropositivity: 1
Reflectivity (%): N/A
Refractive Index: 1.000427
Electrons: 36
Protons: 36
Neutrons: 48
Electron Configuration: [Ar] 3d10 4s2 4p6
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: 116±4 pm
Covalent Radius (Å): 1.16
Van der Waals Radius: 202 pm
Oxidation States: 2, 1, 0
Phase: Gas
Crystal Structure: cubic face-centered
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) Not stable
1st Ionization Energy: 1350.77 kJ·mol-1
2nd Ionization Energy: 2350.39 kJ·mol-1
3rd Ionization Energy: 3565.16 kJ·mol-1
CAS Number: 7439-90-9
EC Number: N/A
MDL Number: MFCD00151310
Beilstein Number: N/A
SMILES Identifier: [Kr]
InChI Identifier: InChI=1S/Kr
PubChem CID: 5416
ChemSpider ID: 5223
Earth - Total: 0.0236E-8 cm^3/g
Mercury - Total: N/A
Venus - Total: 2.30E-8 cm^3/g
Earth - Seawater (Oceans), ppb by weight: 0.21
Earth - Seawater (Oceans), ppb by atoms: 0.016
Earth -  Crust (Crustal Rocks), ppb by weight: 0.15
Earth -  Crust (Crustal Rocks), ppb by atoms: 0.04
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: 40
Universe, ppb by atom: 0.06
Discovered By: William Ramsay and Morris Travers
Discovery Date: 1898
First Isolation: William Ramsay and Morris Travers (1898)

Health, Safety & Transportation Information for Krypton

Krypton is not toxic and is chemically inert, and thus poses minimal environmental or health threats. At room temperature, krypton is typically only harmful when its presence leads to displacement of oxygen in the air, creating potential for asphyxiation.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Warning
Hazard Statements H280
Hazard Codes N/A
Risk Codes N/A
Safety Precautions N/A
RTECS Number N/A
Transport Information N/A
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)
Gas Cylinder - Gases Under Pressure

Krypton Isotopes

Naturally occurring krypton has six stable isotopes: 78Kr, 80Kr, 82Kr, 83Kr, 84Kr, and 86Kr.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
69Kr68.96518(43)#32(10) msß+ to 69Br5/2-#N/A549.64-
70Kr69.95526(41)#52(17) msß+ to 70Br0+N/A567.04-
71Kr70.94963(70)100(3) msß+ to 71Br; ß+ + p to 70Se(5/2)-N/A580.71-
72Kr71.942092(9)17.16(18) sß+ to 72Br0+N/A595.31-
73Kr72.939289(7)28.6(6) sß+ to 73Br; ß+ + p to 72Se3/2-N/A606.18-
74Kr73.9330844(22)11.5 minEC to 74Br0+N/A619.85-
75Kr74.930946(9)4.3 minEC to 75Br5/2+N/A630.72-
76Kr75.925910(4)14.8 hEC to 76Br0+N/A643.46-
77Kr76.9246700(21)1.24 hEC to 77Br5/2+N/A652.47-
78Kr77.9203648(12)Observationally Stable-0+N/A664.280.35
79Kr78.920082(4)1.455 dEC to 79Br1/2-N/A672.35-
81Kr80.9165920(21)210000 yEC to 81Br7/2+N/A692.24-
85Kr84.9125273(21)10.73 yß- to 85Rb9/2+1.005728.28-
86Kr85.91061073(11)Observationally Stable-0+N/A738.2217.3
87Kr86.91335486(29)1.27 hß- to 87Rb5/2+-1.018743.51-
88Kr87.914447(14)2.84 hß- to 88Rb0+N/A750.65-
89Kr88.91763(6)3.15 minß- to 89Rb3/2(+#)N/A755.94-
90Kr89.919517(20)32.32(9) sß- to 90Rb0+N/A762.15-
91Kr90.92345(6)8.57(4) sß- to 91Rb5/2(+)N/A766.5-
92Kr91.926156(13)1.840(8) sß- to 92Rb; ß- + n to 91Rb0+N/A771.79-
93Kr92.93127(11)1.286(10) sß- to 93Rb; ß- + n to 92Rb1/2+N/A775.21-
94Kr93.93436(32)#210(4) msß- to 94Rb; ß- + n to 93Rb0+N/A780.49-
95Kr94.93984(43)#114(3) msß- to 95Rb1/2(+)N/A783.91-
96Kr95.94307(54)#80(7) msß- to 96Rb0+N/A788.26-
97Kr96.94856(54)#63(4) msß- to 97Rb; ß- + n to 96Rb3/2+#N/A791.69-
98Kr97.95191(64)#46(8) msUnknown0+N/A796.97-
99Kr98.95760(64)#40(11) msUnknown(3/2+)#N/A799.46-
100Kr99.96114(54)#10# ms [>300 ns]Unknown0+N/A803.81-
100Kr100>635 nsß- + 2n to 99Rb; ß- + n to 100Rb; ß- to 101Rb; N/AN/AN/A-