# Isotopes of potassium > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Isotopes_of_potassium > Markdown URL: https://mediated.wiki/source/Isotopes_of_potassium.md > Source: https://en.wikipedia.org/wiki/Isotopes_of_potassium > Source revision: 1348859093 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|none}} {{Infobox potassium isotopes}} [Potassium](/source/Potassium) ({{chem||19|K}}) has 25 known [isotope](/source/isotope)s from {{chem|34|K}} to {{chem|57|K}} as well as {{chem|31|K}}, as well as an unconfirmed report of {{chem|59|K}}.{{cite journal |last1=Neufcourt |first1=Léo |last2=Cao |first2=Yuchen |last3=Nazarewicz |first3=Witold |last4=Olsen |first4=Erik |last5=Viens |first5=Frederi |title=Neutron Drip Line in the Ca Region from Bayesian Model Averaging |journal=Physical Review Letters |date=14 February 2019 |volume=122 |issue=6 |article-number=062502 |doi=10.1103/PhysRevLett.122.062502 |pmid=30822058 |arxiv=1901.07632 |bibcode=2019PhRvL.122f2502N |display-authors=3}} Three of those isotopes occur naturally: the two stable forms {{chem|39|K}} (93.26%) and {{chem|41|K}} (6.72%), and the long-lived radioisotope [{{chem|40|K}}](/source/Potassium-40) (0.012%). Naturally occurring radioactive {{chem|40|K}} decays with a [half-life](/source/half-life) of 1.248×109 years. 89% of those decays are to stable [{{chem|40|Ca}}](/source/Calcium-40) by [beta decay](/source/beta_decay), whilst 11% are to [{{chem|40|Ar}}](/source/Argon-40) by either [electron capture](/source/electron_capture) or [positron emission](/source/positron_emission). This latter decay branch has produced an isotopic abundance of argon on Earth which differs greatly from that seen in [gas giant](/source/gas_giant)s and stellar spectra. {{chem|40|K}} has the longest known half-life for any positron-emitting [nuclide](/source/nuclide).Of longer ones, only 50V and 138La are theoretically capable of it, but they are still more forbidden and have very low energy release. The long half-life of this [primordial radioisotope](/source/primordial_radioisotope) is caused by a highly [spin-forbidden transition](/source/selection_rule): {{chem|40|K}} has a [nuclear spin](/source/nuclear_spin) of 4, while both of its decay daughters are [even–even isotopes](/source/even_and_odd_atomic_nuclei) with spins of 0. {{chem|40|K}} occurs in natural potassium in sufficient quantity that large bags of [potassium chloride](/source/potassium_chloride) commercial [salt substitute](/source/salt_substitute)s can be used as a [radioactive source](/source/radioactive_source) for classroom demonstrations.{{citation needed|date=May 2018}} {{chem|40|K}} is the largest source of natural radioactivity in healthy animals and humans, greater even than [{{chem|14|C}}](/source/carbon-14). In a human body of 70 kg mass, about 4300 nuclei of {{chem|40|K}} decay per second.{{cite web | vauthors = Rowland RE | url = http://www.rerowland.com/BodyActivity.htm | title = The Radioactivity of the Normal Adult Body | archive-url = https://web.archive.org/web/20110205025628/http://www.rerowland.com/BodyActivity.htm | archive-date=2011-02-05 | work = rerowland.com }} The decay of {{chem|40|K}} to {{chem|40|Ar}} is used in [potassium-argon dating](/source/potassium-argon_dating) of rocks. [Mineral](/source/Mineral)s are dated by measurement of the concentration of potassium and the amount of radiogenic {{chem|40|Ar}} that has accumulated. {{chem|40|K}} has also been extensively used as a [radioactive tracer](/source/radioactive_tracer) in studies of [weathering](/source/weathering).{{citation needed|date=April 2020}} All other potassium isotopes have half-lives under a day, most under a minute. The unbound {{chem|31|K}} was discovered in 2019 and emits ''three'' [protons](/source/proton_emission); its half-life was measured to be shorter than 10 [picosecond](/source/picosecond)s.{{cite journal |title=A peculiar atom shakes up assumptions of nuclear structure |journal=Nature |volume=573 |issue=7773 |page=167 |date=6 September 2019 |doi=10.1038/d41586-019-02655-9 |pmid=31506620 |bibcode=2019Natur.573T.167. |doi-access=free }}{{cite journal |doi=10.1103/PhysRevLett.123.092502 |pmid=31524489 |journal=Physical Review Letters |volume=123 |issue=9 |article-number=092502 |last=Kostyleva |first=D. |display-authors=et al. |title=Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope 31K by Measuring Its Three-Proton Decay |date=2019|bibcode=2019PhRvL.123i2502K |arxiv=1905.08154 |s2cid=159041565 }} Stable potassium isotopes have been used for several [nutrient cycling](/source/nutrient_cycling) studies since potassium is a [macronutrient](/source/macronutrient_(ecology)) required for life.{{Cite web |date=June 2022 |title=Soil potassium isotope composition during four million years of ecosystem development in Hawaiʻi |url=https://par.nsf.gov/servlets/purl/10389596 |website=par.nsf.gov}} == List of isotopes == {{Anchor|Potassium-32|Potassium-32m|Potassium-33|Potassium-58}} {{Isotopes table |symbol=K |refs=NUBASE2020, AME2020 II, IsotopeFRIB, IsomerFRIB |notes=m, unc(), hl#, mass#, exen#, spin(), spin#, daughter-st, daughter-hst, discoveryname }} |-id=Potassium-31 | {{chem|31|K}} | style="text-align:right" | 19 | style="text-align:right" | 12 | 31.03678(32)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/31.pdf 2019] | <10 ps | p | 30Ar | 3/2+# | | |-id=Potassium-34 | 34K{{cite journal | last1=Dronchi | first1=N. | last2=Charity | first2=R. J. | last3=Sobotka | first3=L. G. | last4=Brown | first4=B. A. | last5=Weisshaar | first5=D. | last6=Gade | first6=A. | last7=Brown | first7=K. W. | last8=Reviol | first8=W. | last9=Bazin | first9=D. | last10=Farris | first10=P. J. | last11=Hill | first11=A. M. | last12=Li | first12=J. | last13=Longfellow | first13=B. | last14=Rhodes | first14=D. | last15=Paneru | first15=S. N. | last16=Gillespie | first16=S. A. | last17=Anthony | first17=A. K. | last18=Rubino | first18=E. | last19=Biswas | first19=S. | title=Evolution of shell gaps in the neutron-poor calcium region from invariant-mass spectroscopy of 37,38Sc, 35Ca, and 34K | journal=Physical Review C | volume=110 | issue=3 | date=2024-09-12 | issn=2469-9985 | doi=10.1103/PhysRevC.110.L031302 | osti=2441307 }} | style="text-align:right" | 19 | style="text-align:right" | 15 | 33.998404(18) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/34.pdf 2024] | | p | 33Ar | | | |-id=Potassium-35 | rowspan=2|35K | rowspan=2 style="text-align:right" | 19 | rowspan=2 style="text-align:right" | 16 | rowspan=2|34.98800541(55) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/35.pdf 1976] | rowspan=2|175.2(19) ms | [β+](/source/beta_decay) (99.63%) | 35Ar | rowspan=2|3/2+ | rowspan=2| | rowspan=2| |- | β+, p (0.37%) | 34Cl |-id=Potassium-36 | rowspan=3|36K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 17 | rowspan=3|35.98130189(35) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/36.pdf 1967] | rowspan=3|341(3) ms | β+ (99.95%) | '''36Ar''' | rowspan=3|2+ | rowspan=3| | rowspan=3| |- | β+, p (0.048%) | '''35Cl''' |- | β+, [α](/source/alpha_decay) (0.0034%) | '''32S''' |-id=Potassium-37 | 37K | style="text-align:right" | 19 | style="text-align:right" | 18 | 36.97337589(10) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/37.pdf 1958] | 1.23651(94) s | β+ | 37Ar | 3/2+ | | |-id=Potassium-38 | 38K | style="text-align:right" | 19 | style="text-align:right" | 19 | 37.96908111(21) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/38.pdf 1937] | 7.651(19) min | β+ | '''38Ar''' | 3+ | | |-id=Potassium-38m1 | rowspan=2 style="text-indent:1em" | 38m1K | rowspan=2 colspan="3" style="text-indent:2em" | 130.15(4) keV | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/19/38K-1.pdf 1953] | rowspan=2|924.35(12) ms | β+ (99.97%) | '''38Ar''' | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | [IT](/source/Isomeric_transition) (0.0330%) | 38K |-id=Potassium-38m2 | style="text-indent:1em" | 38m2K | colspan="3" style="text-indent:2em" | 3458.10(17) keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/19/38K-2.pdf 1974] | 21.95(11) μs | IT | 38K | (7)+ | | |-id=Potassium-39 | 39K | style="text-align:right" | 19 | style="text-align:right" | 20 | 38.9637064848(49) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/39.pdf 1918] | colspan=3 align=center|'''Stable''' | 3/2+ | 0.932581(44) | |- | rowspan=3|[40K](/source/potassium-40)Used in [potassium-argon dating](/source/potassium-argon_dating)[Primordial](/source/Primordial_nuclide) [radionuclide](/source/radionuclide) | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 21 | rowspan=3|39.963998165(60) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/40.pdf 1935] | rowspan=3|1.248(3)×109 y | β− (89.28%) | '''40Ca''' | rowspan=3|4− | rowspan=3|1.17(1)×10−4 | rowspan=3| |- | [EC](/source/Electron_capture) (10.72%) | rowspan=2|'''40Ar''' |- |- | β+ (0.001%){{Cite journal | volume = 126 | issue = 5 | page = 1818 | last1 = Engelkemeir | first1 = D. W. | last2 = Flynn | first2 = K. F. | last3 = Glendenin | first3 = L. E. | title = Positron Emission in the Decay of K40 | journal = Physical Review | date = 1962 | doi = 10.1103/PhysRev.126.1818 |bibcode = 1962PhRv..126.1818E }} |-id=Potassium-40m | style="text-indent:1em" | 40mK | colspan="3" style="text-indent:2em" | 1643.638(11) keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/19/40K-1.pdf 1968] | 336(12) ns | IT | '''''40K''''' | 0+ | | |-id=Potassium-41 | 41K | style="text-align:right" | 19 | style="text-align:right" | 22 | 40.9618252561(40) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/41.pdf 1921] | colspan=3 align=center|'''Stable''' | 3/2+ | 0.067302(44) | |-id=Potassium-42 | 42K | style="text-align:right" | 19 | style="text-align:right" | 23 | 41.96240231(11) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/42.pdf 1935] | 12.355(7) h | β− | '''42Ca''' | 2− | | |-id=Potassium-43 | 43K | style="text-align:right" | 19 | style="text-align:right" | 24 | 42.96073470(44) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/43.pdf 1949] | 22.3(1) h | β− | '''43Ca''' | 3/2+ | | |-id=Potassium-43m | style="text-indent:1em" | 43mK | colspan=3 style="text-indent:2em" | 738.30(6) keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/19/43K-1.pdf 1975] | 200(5) ns | IT | 43K | 7/2− | | |-id=Potassium-44 | 44K | style="text-align:right" | 19 | style="text-align:right" | 25 | 43.96158698(45) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/44.pdf 1954] | 22.13(19) min | β− | '''44Ca''' | 2− | | |-id=Potassium-45 | 45K | style="text-align:right" | 19 | style="text-align:right" | 26 | 44.96069149(56) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/45.pdf 1964] | 17.8(6) min | β− | 45Ca | 3/2+ | | |-id=Potassium-46 | 46K | style="text-align:right" | 19 | style="text-align:right" | 27 | 45.96198158(78) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/46.pdf 1965] | 96.30(8) s | β− | '''46Ca''' | 2− | | |-id=Potassium-47 | 47K | style="text-align:right" | 19 | style="text-align:right" | 28 | 46.9616616(15) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/47.pdf 1964] | 17.38(3) s | β− | 47Ca | 1/2+ | | |-id=Potassium-48 | rowspan=2|48K | rowspan=2 style="text-align:right" | 19 | rowspan=2 style="text-align:right" | 29 | rowspan=2|47.96534118(83) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/48.pdf 1972] | rowspan=2|6.83(14) s | β− (98.86%) | '''''48Ca''''' | rowspan=2|1− | rowspan=2| | rowspan=2| |- | β−, [n](/source/neutron_emission) (1.14%) | 47Ca |-id=Potassium-49 | rowspan=2|49K | rowspan=2 style="text-align:right" | 19 | rowspan=2 style="text-align:right" | 30 | rowspan=2|48.96821075(86) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/49.pdf 1972] | rowspan=2|1.26(5) s | β−, n (86%) | '''''48Ca''''' | rowspan=2|1/2+ | rowspan=2| | rowspan=2| |- | β− (14%) | 49Ca |-id=Potassium-50 | rowspan=3|50K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 31 | rowspan=3|49.9723800(83) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/50.pdf 1972] | rowspan=3|472(4) ms | β− (71.4%) | 50Ca | rowspan=3|0− | rowspan=3| | rowspan=3| |- | β−, n (28.6%) | 49Ca |- | β−, 2n? | '''''48Ca''''' |-id=Potassium-50m | style="text-indent:1em" | 50mK | colspan=3 style="text-indent:2em" | 172.0(4) keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/19/50K-1.pdf 2010] | 125(40) ns | IT | 50K | (2−) | | |-id=Potassium-51 | rowspan=3|51K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 32 | rowspan=3|50.975828(14) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/51.pdf 1983] | rowspan=3|365(5) ms | β−, n (65%) | 50Ca | rowspan=3|3/2+ | rowspan=3| | rowspan=3| |- | β− (35%) | 51Ca |- | β−, 2n? | 49Ca |-id=Potassium-52 | rowspan=3|52K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 33 | rowspan=3|51.981602(36) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/52.pdf 1983] | rowspan=3|110(4) ms | β−, n (72.2%) | 51Ca | rowspan=3|2−# | rowspan=3| | rowspan=3| |- | β− (25.5%) | 52Ca |- | β−, 2n (2.3%) | 50Ca |-id=Potassium-53 | rowspan=3|53K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 34 | rowspan=3|52.98680(12) | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/53.pdf 1983] | rowspan=3|30(5) ms | β−, n (64%) | 52Ca | rowspan=3|3/2+ | rowspan=3| | rowspan=3| |- | β− (26%) | 53Ca |- | β−, 2n (10%) | 51Ca |-id=Potassium-54 | rowspan=3|54K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 35 | rowspan=3|53.99447(43)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/54.pdf 1983] | rowspan=3|10(5) ms | β− | 54Ca | rowspan=3|2−# | rowspan=3| | rowspan=3| |- | β−, n? | 53Ca |- | β−, 2n? | 52Ca |-id=Potassium-55 | rowspan=3|55K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 36 | rowspan=3|55.00051(54)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/55.pdf 2009] | rowspan=3|10# ms
[>620 ns] | β−? | 55Ca | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β−, n? | 54Ca |- | β−, 2n? | 53Ca |-id=Potassium-56 | rowspan=3|56K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 37 | rowspan=3|56.00857(64)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/56.pdf 2009] | rowspan=3|5# ms
[>620 ns] | β−? | 56Ca | rowspan=3|2−# | rowspan=3| | rowspan=3| |- | β−, n? | 55Ca |- | β−, 2n? | 54Ca |-id=Potassium-57 | rowspan=3|57K | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 38 | rowspan=3|57.01517(64)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/57.pdf 2018] | rowspan=3|2# ms
[>400 ns] | β−? | 57Ca | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β−, n? | 56Ca |- | β−, 2n? | 55Ca |-id=Potassium-59 | rowspan=3|59KDiscovery of this isotope is unconfirmed. | rowspan=3 style="text-align:right" | 19 | rowspan=3 style="text-align:right" | 40 | rowspan=3|59.03086(86)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/19/59.pdf 2018] | rowspan=3|1# ms
[>400 ns] | β−? | 59Ca | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β−, n? | 58Ca |- | β−, 2n? | 57Ca {{Isotopes table/footer}} == See also == *[Banana equivalent dose](/source/Banana_equivalent_dose) '''Daughter products other than potassium''' * [Isotopes of calcium](/source/Isotopes_of_calcium) * [Isotopes of argon](/source/Isotopes_of_argon) * [Isotopes of chlorine](/source/Isotopes_of_chlorine) * [Isotopes of sulfur](/source/Isotopes_of_sulfur) == References == {{Reflist}} {{Navbox element isotopes}} Category:Isotopes of potassium Category:Potassium Potassium --- Adapted from the Wikipedia article [Isotopes of potassium](https://en.wikipedia.org/wiki/Isotopes_of_potassium) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Isotopes_of_potassium?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.