Krypton
Krypton (Kr) is element 36, a noble gas in group 18, period 4, with an atomic mass of 83.798 u. It is a gas at room temperature and boils at −153.22 °C. Its electron configuration is [Ar] 4s² 3d¹⁰ 4p⁶.
Krypton is a colorless, odorless noble gas present in only trace amounts in Earth's atmosphere, which is exactly why it eluded chemists for so long. Like the other noble gases, it's extremely unreactive, but it still found a surprisingly precise role in science and industry.
- Group · Period
- 18 · 4
- At room temp
- gas
- Melts at
- 115.79 K
- Density
- 3.733 g/L
- Discovered
- 1898
Key facts about krypton
Quick answers, built from the sourced data in the property tables.
- What is the electron configuration of krypton?
- The electron configuration of krypton is [Ar] 4s² 3d¹⁰ 4p⁶. Written out in full, that is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶.
- What is the density of krypton?
- Krypton is a gas, so its density is usually given in grams per litre: 3.733 g/L at STP (0 °C and 1 atm), which is 0.003733 g/cm³.
- What are the melting and boiling points of krypton?
- Krypton melts at 115.79 K (−157.36 °C, −251.25 °F) and boils at 119.93 K (−153.22 °C, −243.8 °F).
- How many stable isotopes does krypton have?
- Krypton has 6 stable isotopes: Kr-78 (0.355%), Kr-80 (2.286%), Kr-82 (11.593%), Kr-83 (11.5%), Kr-84 (56.987%), and Kr-86 (17.279%). Percentages are natural abundances.
Uses
Krypton gas is used to fill certain specialty light bulbs, including some high-performance incandescent and fluorescent lamps, because it produces a brighter, whiter light than ordinary air-filled bulbs and allows thinner filaments to last longer. It’s also used in some photographic flash equipment and in some types of lasers. In construction, krypton is sometimes used instead of argon between the panes of high-efficiency double- or triple-glazed windows, since its lower thermal conductivity further reduces the amount of heat that passes through the glass.
For decades, krypton also played a foundational role in measurement science: from 1960 until 1983, the international definition of the meter was based on a precise wavelength of light emitted by krypton-86 atoms, replacing an older physical reference bar and giving scientists a far more reproducible standard, before the definition was updated again to be based on the speed of light.
History
Krypton was discovered in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers, working in London. Having already identified argon a few years earlier, the pair suspected other unknown gases might be hiding in air and began evaporating liquid air and carefully examining the residues left behind. Among these residues they found a new, extremely unreactive gas that gave off a distinctive spectral signature under electrical discharge. They named it krypton, from the Greek word kryptos meaning hidden, a nod to how thoroughly it had escaped detection despite being present in every breath of air.
Fun facts
- Krypton was named from the Greek word 'kryptos,' meaning hidden, because it was so scarce and difficult to isolate from air.
- From 1960 to 1983, the meter was officially defined using a specific wavelength of light emitted by krypton-86 atoms.
- Krypton gas is used to fill some high-efficiency window panes, where it slows heat transfer better than ordinary air.
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Frequently asked questions
How rare is krypton, really?
It's only a tiny trace component of the air we breathe, far less abundant than nitrogen, oxygen or even argon. That scarcity is exactly why it wasn't discovered until 1898, when Earth's atmosphere had already been fairly thoroughly studied.
Is Superman's home planet Krypton named after the element?
Most accounts of the comic's history suggest the element's name was borrowed for its exotic, scientific sound rather than for any chemical property, though the original creators never gave a detailed explanation. Either way, the fictional planet has no real connection to the chemistry of the element beyond sharing its name.
What is krypton actually used for today?
Its main practical roles are in specialty lighting, where krypton gas fill produces a brighter, whiter light in some bulbs and photographic flashes, and in insulated window glazing, where its low thermal conductivity helps reduce heat loss compared to air.
Compounds
1 notable compound containing Kr
- KrF2halide
Krypton difluoride
A rare, thermally unstable compound of a noble gas, made by exposing krypton and fluorine to electrical discharge or radiation at very low temperatures; it decomposes back to its elements near room temperature.
Used for: Laboratory demonstration of noble-gas reactivity and a powerful fluorinating agent
Isotopes
36 known isotopes
Swipe to see all columns →
| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width | Spin/parity | Magnetic moment | Quadrupole moment |
|---|---|---|---|---|---|---|---|---|---|
| Kr-78 stable | 0.355% | Stable | — | -74,178.28 keV | 8,661.24 keV | — | 0+ | 1.8 μN | — |
| Kr-80 stable | 2.286% | Stable | — | -77,893.46 keV | 8,692.93 keV | — | 0+ | — | — |
| Kr-82 stable | 11.593% | Stable | — | -80,591.8 keV | 8,710.68 keV | — | 0+ | 0.8 μN | — |
| Kr-83 stable | 11.5% | Stable | — | -79,990.64 keV | 8,695.73 keV | — | 9/2+ | -0.97073 μN | 0.259 b |
| Kr-84 stable | 56.987% | Stable | — | -82,439.35 keV | 8,717.45 keV | — | 0+ | — | — |
| Kr-86 stable | 17.279% | Stable | — | -83,265.68 keV | 8,712.03 keV | — | 0+ | 2.2 μN | — |
| Kr-67 | — | 7.4 ms | Electron capture (63%), Electron capture / beta-plus decay (63%), Two-proton emission (37%) | -15,552 keV | 7,883 keV | 6.17 × 10-14 eV | — | — | — |
| Kr-68 | — | 21.6 ms | Electron capture / beta-plus decay (100%), ECP (89%) | -25,626 keV | 8,034 keV | 2.11 × 10-14 eV | 0+ | — | — |
| Kr-69 | — | 28 ms | Electron capture / beta-plus decay (100%), Beta-plus, proton emission (99%) | -32,140 keV | 8,129 keV | 1.63 × 10-14 eV | (5/2-) | — | — |
| Kr-70 | — | 40 ms | Electron capture / beta-plus decay (100%), ECP (1.3%) | -41,100 keV | 8,256 keV | 1.14 × 10-14 eV | 0+ | — | — |
| Kr-71 | — | 94.9 ms | Electron capture / beta-plus decay (100%), ECP (3.06%) | -46,327.21 keV | 8,327.13 keV | 4.81 × 10-15 eV | (5/2)- | — | — |
| Kr-72 | — | 17.1 s | Electron capture / beta-plus decay (100%), ECP (0.000001%) | -53,940.58 keV | 8,429.32 keV | 2.67 × 10-17 eV | 0+ | — | — |
| Kr-73 | — | 27.3 s | Electron capture / beta-plus decay (100%), ECP (0.25%) | -56,551.76 keV | 8,460.18 keV | 1.67 × 10-17 eV | (3/2)- | — | — |
| Kr-74 | — | 11.50 m | Electron capture / beta-plus decay (100%) | -62,331.84 keV | 8,533.04 keV | 6.61 × 10-19 eV | 0+ | — | — |
| Kr-75 | — | 4.60 m | Electron capture / beta-plus decay (100%) | -64,323.63 keV | 8,553.44 keV | 1.65 × 10-18 eV | 5/2+ | -0.531 μN | 1.137 b |
| Kr-76 | — | 14.8 h | Electron capture / beta-plus decay (100%) | -69,013.71 keV | 8,608.81 keV | 8.56 × 10-21 eV | 0+ | — | — |
| Kr-77 | — | 71.25 m | Electron capture / beta-plus decay (100%) | -70,169.45 keV | 8,616.84 keV | 1.07 × 10-19 eV | 5/2+ | -0.583 μN | 0.948 b |
| Kr-79 | — | 35.04 h | Electron capture / beta-plus decay (100%) | -74,442.29 keV | 8,657.11 keV | 3.62 × 10-21 eV | 1/2- | 0.536 μN | — |
| Kr-81 | — | 2.29E+5 Y | Electron capture (100%) | -77,696.2 keV | 8,682.82 keV | 6.31 × 10-29 eV | 7/2+ | -0.907 μN | 0.644 b |
| Kr-85 | — | 10.739 Y | Beta-minus decay (100%) | -81,480.34 keV | 8,698.56 keV | 1.35 × 10-24 eV | 9/2+ | -1.0055 μN | 0.443 b |
| Kr-87 | — | 76.3 m | Beta-minus decay (100%) | -80,709.53 keV | 8,675.28 keV | 9.97 × 10-20 eV | 5/2+ | -1.022 μN | -0.3 b |
| Kr-88 | — | 2.825 h | Beta-minus decay (100%) | -79,691.3 keV | 8,656.85 keV | 4.49 × 10-20 eV | 0+ | — | — |
| Kr-89 | — | 3.15 m | Beta-minus decay (100%) | -76,535.8 keV | 8,614.82 keV | 2.41 × 10-18 eV | 3/2(+) | -0.33 μN | 0.166 b |
| Kr-90 | — | 32.32 s | Beta-minus decay (100%) | -74,959.26 keV | 8,591.26 keV | 1.41 × 10-17 eV | 0+ | — | — |
| Kr-91 | — | 8.57 s | Beta-minus decay (100%) | -70,973.97 keV | 8,541.75 keV | 5.32 × 10-17 eV | 5/2(+) | -0.583 μN | 0.303 b |
| Kr-92 | — | 1.840 s | Beta-minus decay (100%), Beta-minus, neutron emission (0.0332%) | -68,769.33 keV | 8,512.68 keV | 2.48 × 10-16 eV | 0+ | — | — |
| Kr-93 | — | 1.286 s | Beta-minus decay (100%), Beta-minus, neutron emission (1.95%) | -64,136 keV | 8,458.11 keV | 3.55 × 10-16 eV | 1/2+ | -0.413 μN | — |
| Kr-94 | — | 212 ms | Beta-minus decay (100%), Beta-minus, neutron emission (1.11%) | -61,347.78 keV | 8,424.33 keV | 2.15 × 10-15 eV | 0+ | — | -0.5 b |
| Kr-95 | — | 0.114 s | Beta-minus decay (100%), Beta-minus, neutron emission (2.87%) | -56,158.92 keV | 8,366 keV | 4.00 × 10-15 eV | 1/2(+) | -0.41 μN | — |
| Kr-96 | — | 80 ms | Beta-minus decay (100%), Beta-minus, neutron emission (3.7%) | -53,081.68 keV | 8,330.87 keV | 5.70 × 10-15 eV | 0+ | — | — |
| Kr-97 | — | 63 ms | Beta-minus decay (100%), Beta-minus, neutron emission (6.7%) | -47,423.5 keV | 8,269.86 keV | 7.24 × 10-15 eV | (3/2+) | — | — |
| Kr-98 | — | 43 ms | Beta-minus decay (100%), Beta-minus, neutron emission (7%), B-2N | -44,120 keV | 8,234 keV | 1.06 × 10-14 eV | 0+ | — | — |
| Kr-99 | — | 13 ms | Beta-minus decay (100%), Beta-minus, neutron emission (11%) | -38,400 keV | 8,175 keV | 3.51 × 10-14 eV | — | — | — |
| Kr-100 | — | 7 ms | Beta-minus decay (100%), Beta-minus, neutron emission, B-2N | -34,470 keV | 8,134 keV | 6.52 × 10-14 eV | 0+ | — | — |
| Kr-101 | — | 635 ns | Beta-minus decay, Beta-minus, neutron emission, B-2N | -28,580 keV | 8,075 keV | 7.18 × 10-10 eV | — | — | — |
| Kr-102 | — | — | Beta-minus decay (100%), Beta-minus, neutron emission, B-2N | — | — | — | 0+ | — | — |
Spin/parity describes the nucleus's intrinsic angular momentum and symmetry. Magnetic moment (in nuclear magnetons, μN) and quadrupole moment (in barns, b) describe the shape of the nucleus's charge distribution — a nonzero quadrupole moment means the nucleus isn't perfectly spherical. These are only measured for a subset of isotopes, mostly stable or long-lived ones, so many rows show "—" rather than a value.