Isotopes of potassium: Difference between revisions
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[[Potassium]] ({{chem||19|K}}) has 25 known '''[[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}}.<ref name="neufcourt2019">{{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 |page=062502 |doi=10.1103/PhysRevLett.122.062502 |pmid=30822058 |arxiv=1901.07632 |bibcode=2019PhRvL.122f2502N |display-authors=3}}</ref> Three of those isotopes occur naturally: the two stable forms {{chem|39|K}} (93.3%) and {{chem|41|K}} (6.7%), and a very long-lived radioisotope [[Potassium-40|{{chem|40|K}}]] (0.012%) | [[Potassium]] ({{chem||19|K}}) has 25 known '''[[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}}.<ref name="neufcourt2019">{{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 |page=062502 |doi=10.1103/PhysRevLett.122.062502 |pmid=30822058 |arxiv=1901.07632 |bibcode=2019PhRvL.122f2502N |display-authors=3}}</ref> Three of those isotopes occur naturally: the two stable forms {{chem|39|K}} (93.3%) and {{chem|41|K}} (6.7%), and a very long-lived radioisotope [[Potassium-40|{{chem|40|K}}]] (0.012%) | ||
Naturally occurring radioactive {{chem|40|K}} decays with a [[half-life]] of 1.248×10<sup>9</sup> years. 89% of those decays are to stable [[Calcium-40|{{chem|40|Ca}}]] by [[beta decay]], whilst 11% are to [[Argon-40|{{chem|40|Ar}}]] by either [[electron capture]] or [[positron emission]]. This latter decay branch has produced an isotopic abundance of argon on Earth which differs greatly from that seen in [[gas giant]]s and stellar spectra. {{chem|40|K}} has the longest known half-life for any positron- | Naturally occurring radioactive {{chem|40|K}} decays with a [[half-life]] of 1.248×10<sup>9</sup> years. 89% of those decays are to stable [[Calcium-40|{{chem|40|Ca}}]] by [[beta decay]], whilst 11% are to [[Argon-40|{{chem|40|Ar}}]] by either [[electron capture]] or [[positron emission]]. This latter decay branch has produced an isotopic abundance of argon on Earth which differs greatly from that seen in [[gas giant]]s and stellar spectra. {{chem|40|K}} has the longest known half-life for any positron-emitting [[nuclide]].<ref>Of longer ones, only <sup>50</sup>V and <sup>138</sup>La are theoretically capable of it, but they are still more forbidden and have very low energy release.</ref> The long half-life of this [[primordial radioisotope]] is caused by a highly [[selection rule|spin-forbidden transition]]: {{chem|40|K}} has a [[nuclear spin]] of 4, while both of its decay daughters are [[even and odd atomic nuclei|even–even isotopes]] with spins of 0. | ||
{{chem|40|K}} occurs in natural potassium in sufficient quantity that large bags of [[potassium chloride]] commercial [[salt substitute]]s can be used as a [[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 [[carbon-14|{{chem|14|C}}]]. In a human body of 70 kg mass, about 4,400 nuclei of {{chem|40|K}} decay per second.<ref>{{Cite web | url=http://www.fas.harvard.edu/~scdiroff/lds/QuantumRelativity/RadioactiveHumanBody/RadioactiveHumanBody.html | title=Radioactive Human Body |access-date=2011-05-18}}</ref> | {{chem|40|K}} occurs in natural potassium in sufficient quantity that large bags of [[potassium chloride]] commercial [[salt substitute]]s can be used as a [[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 [[carbon-14|{{chem|14|C}}]]. In a human body of 70 kg mass, about 4,400 nuclei of {{chem|40|K}} decay per second.<ref>{{Cite web | url=http://www.fas.harvard.edu/~scdiroff/lds/QuantumRelativity/RadioactiveHumanBody/RadioactiveHumanBody.html | title=Radioactive Human Body |access-date=2011-05-18}}</ref> | ||
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| '''<sup>42</sup>Ca''' | | '''<sup>42</sup>Ca''' | ||
| 2− | | 2− | ||
| | | | ||
| | | | ||
|-id=Potassium-43 | |-id=Potassium-43 | ||
Latest revision as of 14:08, 25 June 2025
Template:Short description Template:Infobox potassium isotopes Potassium (Template:Chem/link) has 25 known isotopes from Template:Chem/link to Template:Chem/link as well as Template:Chem/link, as well as an unconfirmed report of Template:Chem/link.[1] Three of those isotopes occur naturally: the two stable forms Template:Chem/link (93.3%) and Template:Chem/link (6.7%), and a very long-lived radioisotope [[Potassium-40|Template:Chem/link]] (0.012%)
Naturally occurring radioactive Template:Chem/link decays with a half-life of 1.248×109 years. 89% of those decays are to stable [[Calcium-40|Template:Chem/link]] by beta decay, whilst 11% are to [[Argon-40|Template:Chem/link]] by either electron capture or positron emission. This latter decay branch has produced an isotopic abundance of argon on Earth which differs greatly from that seen in gas giants and stellar spectra. Template:Chem/link has the longest known half-life for any positron-emitting nuclide.[2] The long half-life of this primordial radioisotope is caused by a highly spin-forbidden transition: Template:Chem/link has a nuclear spin of 4, while both of its decay daughters are even–even isotopes with spins of 0.
Template:Chem/link occurs in natural potassium in sufficient quantity that large bags of potassium chloride commercial salt substitutes can be used as a radioactive source for classroom demonstrations.Script error: No such module "Unsubst". Template:Chem/link is the largest source of natural radioactivity in healthy animals and humans, greater even than [[carbon-14|Template:Chem/link]]. In a human body of 70 kg mass, about 4,400 nuclei of Template:Chem/link decay per second.[3]
The decay of Template:Chem/link to Template:Chem/link is used in potassium-argon dating of rocks. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic Template:Chem/link that has accumulated. Typically, the method assumes that the rocks contained no argon at the time of formation and all subsequent radiogenic argon (i.e., Template:Chem/link) was retained.Script error: No such module "Unsubst". Template:Chem/link has also been extensively used as a radioactive tracer in studies of weathering.Script error: No such module "Unsubst".
All other potassium isotopes have half-lives under a day, most under a minute. The least stable is Template:Chem/link, a three-proton emitter discovered in 2019; its half-life was measured to be shorter than 10 picoseconds.[4][5]
Stable potassium isotopes have been used for several nutrient cycling studies since potassium is a macronutrient required for life.[6]
List of isotopes
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Template:Isotopes table
|-id=Potassium-31
| Template:Chem/link[4][5]
| style="text-align:right" | 19
| style="text-align:right" | 12
| 31.03678(32)#
| <10 ps
| 3p
| 28S
| 3/2+#
|
|
|-id=Potassium-34
| 34K[7]
| style="text-align:right" | 19
| style="text-align:right" | 15
| 33.998404(18)
|
| 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|175.2(19) ms
| β+ (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|341(3) ms
| β+ (99.95%)
| 36Ar
| rowspan=3|2+
| rowspan=3|
| rowspan=3|
|-
| β+, p (0.048%)
| 35Cl
|-
| β+, α (0.0034%)
| 32S
|-id=Potassium-37
| 37K
| style="text-align:right" | 19
| style="text-align:right" | 18
| 36.97337589(10)
| 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)
| 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|924.35(12) ms
| β+ (99.97%)
| 38Ar
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| IT (0.0330%)
| 38K
|-id=Potassium-38m2
| style="text-indent:1em" | 38m2K
| colspan="3" style="text-indent:2em" | 3458.10(17) keV
| 21.95(11) μs
| IT
| 38K
| (7)+
|
|
|-id=Potassium-39
| 39K
| style="text-align:right" | 19
| style="text-align:right" | 20
| 38.9637064848(49)
| colspan=3 align=center|Stable
| 3/2+
| 0.932581(44)
|
|-
| rowspan=3|40K[n 1][n 2]
| rowspan=3 style="text-align:right" | 19
| rowspan=3 style="text-align:right" | 21
| rowspan=3|39.963998165(60)
| rowspan=3|1.248(3)×109 y
| β− (89.28%)
| 40Ca
| rowspan=3|4−
| rowspan=3|1.17(1)×10−4
| rowspan=3|
|-
| EC (10.72%)
| rowspan=2|40Ar
|-
|-
| β+ (0.001%)[8]
|-id=Potassium-40m
| style="text-indent:1em" | 40mK
| colspan="3" style="text-indent:2em" | 1643.638(11) keV
| 336(12) ns
| IT
| 40K
| 0+
|
|
|-id=Potassium-41
| 41K
| style="text-align:right" | 19
| style="text-align:right" | 22
| 40.9618252561(40)
| 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)
| 12.355(7) h
| β−
| 42Ca
| 2−
|
|
|-id=Potassium-43
| 43K
| style="text-align:right" | 19
| style="text-align:right" | 24
| 42.96073470(44)
| 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
| 200(5) ns
| IT
| 43K
| 7/2−
|
|
|-id=Potassium-44
| 44K
| style="text-align:right" | 19
| style="text-align:right" | 25
| 43.96158698(45)
| 22.13(19) min
| β−
| 44Ca
| 2−
|
|
|-id=Potassium-45
| 45K
| style="text-align:right" | 19
| style="text-align:right" | 26
| 44.96069149(56)
| 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)
| 96.30(8) s
| β−
| 46Ca
| 2−
|
|
|-id=Potassium-47
| 47K
| style="text-align:right" | 19
| style="text-align:right" | 28
| 46.9616616(15)
| 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|6.83(14) s
| β− (98.86%)
| 48Ca
| rowspan=2|1−
| rowspan=2|
| rowspan=2|
|-
| β−, n (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|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|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
| 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|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|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|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|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|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|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|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|59K[1][n 3]
| rowspan=3 style="text-align:right" | 19
| rowspan=3 style="text-align:right" | 40
| rowspan=3|59.03086(86)#
| rowspan=3|1# ms
[>400 ns]
| β−?
| 59Ca
| rowspan=3|3/2+#
| rowspan=3|
| rowspan=3|
|-
| β−, n?
| 58Ca
|-
| β−, 2n?
| 57Ca
Template:Isotopes table/footer
See also
Daughter products other than potassium
References
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