Potassium () has 26 known isotopes from to , with the exception of still-unknown , as well as an unconfirmed report of . Three of those isotopes occur naturally: the two stable forms (93.3%) and (6.7%), and a very long-lived radioisotope (0.012%) Naturally occurring radioactive decays with a half-life of 1.248×10⁹ years. 89% of those decays are to stable by beta decay, whilst 11% are to by either electron capture or positron emission. has the longest known half life for any positron-emitter

nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state. The word ''nuclide'' was coined by Truman ...

. The long half-life of this primordial radioisotope is caused by a highly spin-forbidden transition: has a

nuclear spin In atomic physics, the spin quantum number is a quantum number (designated ) which describes the intrinsic angular momentum (or spin angular momentum, or simply spin) of an electron or other particle. The phrase was originally used to describe th ...

of 4, while both of its decay daughters are even–even isotopes with spins of 0. occurs in natural potassium in sufficient quantity that large bags of

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...

commercial salt substitutes can be used as a radioactive source for classroom demonstrations. is the largest source of natural radioactivity in healthy animals and humans, greater even than . In a human body of 70 kg mass, about 4,400 nuclei of decay per second. The decay of to is used in potassium-argon dating of rocks. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 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., ) was retained. has also been extensively used as a radioactive tracer in studies of weathering. All other potassium isotopes have half-lives under a day, most under a minute. The least stable is , a three- proton emitter discovered in 2019; its half-life was measured to be shorter than 10

picosecond A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10−12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 ...

s. Various potassium isotopes have been used for

nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...

studies because potassium is a macronutrient required for life.

List of isotopes

, - , , style="text-align:right" , 19 , style="text-align:right" , 12 , , <10 ps , 3p , ²⁸S , , , , - , ³³K , style="text-align:right" , 19 , style="text-align:right" , 14 , 33.00756(21)# , <25 ns , p , ³²Ar , 3/2+# , , , - , ³⁴K , style="text-align:right" , 19 , style="text-align:right" , 15 , 33.99869(21)# , <40 ns , p , ³³Ar , 1+# , , , - , rowspan=2, ³⁵K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 16 , rowspan=2, 34.9880054(6) , rowspan=2, 178(8) ms , β⁺ (99.63%) , ³⁵Ar , rowspan=2, 3/2+ , rowspan=2, , rowspan=2, , - , β⁺, p (.37%) , ³⁴Cl , - , rowspan=3, ³⁶K , rowspan=3 style="text-align:right" , 19 , rowspan=3 style="text-align:right" , 17 , rowspan=3, 35.9813020(4) , rowspan=3, 341(3) ms , β⁺ (99.95%) , ³⁶Ar , rowspan=3, 2+ , rowspan=3, , rowspan=3, , - , β⁺, p (.048%) , ³⁵Cl , - , β⁺, α (.0034%) , ³²S , - , ³⁷K , style="text-align:right" , 19 , style="text-align:right" , 18 , 36.97337589(10) , 1.2365(9) s , β⁺ , ³⁷Ar , 3/2+ , , , - , ³⁸K , style="text-align:right" , 19 , style="text-align:right" , 19 , 37.96908112(21) , 7.636(18) min , β⁺ , ³⁸Ar , 3+ , , , - , style="text-indent:1em" , ^38m1K , colspan="3" style="text-indent:2em" , 130.50(28) keV , 924.46(14) ms , β⁺ , ³⁸Ar , 0+ , , , - , style="text-indent:1em" , ^38m2K , colspan="3" style="text-indent:2em" , 3458.0(2) keV , 21.95(11)

μs A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available. A microsecond is equal to 1000 ...

, IT , ³⁸K , (7+) , , , - , ³⁹K , style="text-align:right" , 19 , style="text-align:right" , 20 , 38.963706487(5) , colspan=3 align=center, Stable , 3/2+ , 0.932581(44) , , - , rowspan=3, ⁴⁰KUsed in potassium-argon dating

Primordial Primordial may refer to: * Primordial era, an era after the Big Bang. See Chronology of the universe * Primordial sea (a.k.a. primordial ocean, ooze or soup). See Abiogenesis * Primordial nuclide, nuclides, a few radioactive, that formed before ...

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...

, rowspan=3 style="text-align:right" , 19 , rowspan=3 style="text-align:right" , 21 , rowspan=3, 39.96399817(6) , 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%) , - , style="text-indent:1em" , ^40mK , colspan="3" style="text-indent:2em" , 1643.639(11) keV , 336(12) ns , IT , ''⁴⁰K'' , 0+ , , , - , ⁴¹K , style="text-align:right" , 19 , style="text-align:right" , 22 , 40.961825258(4) , colspan=3 align=center, Stable , 3/2+ , 0.067302(44) , , - , ⁴²K , style="text-align:right" , 19 , style="text-align:right" , 23 , 41.96240231(11) , 12.355(7) h , β⁻ , ⁴²Ca , 2− , , , - , ⁴³K , style="text-align:right" , 19 , style="text-align:right" , 24 , 42.9607347(4) , 22.3(1) h , β⁻ , ⁴³Ca , 3/2+ , , , - , style="text-indent:1em" , ^43mK , colspan=3 style="text-indent:2em" , 738.30(6) keV , 200(5) ns , IT , ⁴³K , 7/2− , , , - , ⁴⁴K , style="text-align:right" , 19 , style="text-align:right" , 25 , 43.9615870(5) , 22.13(19) min , β⁻ , ⁴⁴Ca , 2− , , , - , ⁴⁵K , style="text-align:right" , 19 , style="text-align:right" , 26 , 44.9606915(6) , 17.8(6) min , β⁻ , ⁴⁵Ca , 3/2+ , , , - , ⁴⁶K , style="text-align:right" , 19 , style="text-align:right" , 27 , 45.9619816(8) , 105(10) s , β⁻ , ⁴⁶Ca , 2− , , , - , ⁴⁷K , style="text-align:right" , 19 , style="text-align:right" , 28 , 46.9616616(15) , 17.50(24) s , β⁻ , ⁴⁷Ca , 1/2+ , , , - , rowspan=2, ⁴⁸K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 29 , rowspan=2, 47.9653412(8) , rowspan=2, 6.8(2) s , β⁻ (98.86%) , ''⁴⁸Ca'' , rowspan=2, 1− , rowspan=2, , rowspan=2, , - , β⁻, n (1.14%) , ⁴⁷Ca , - , rowspan=2, ⁴⁹K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 30 , rowspan=2, 48.9682108(9) , rowspan=2, 1.26(5) s , β⁻, n (86%) , ''⁴⁸Ca'' , rowspan=2, (3/2+) , rowspan=2, , rowspan=2, , - , β⁻ (14%) , ⁴⁹Ca , - , rowspan=2, ⁵⁰K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 31 , rowspan=2, 49.972380(8) , rowspan=2, 472(4) ms , β⁻ (71%) , ⁵⁰Ca , rowspan=2, 0− , rowspan=2, , rowspan=2, , - , β⁻, n (29%) , ⁴⁹Ca , - , style="text-indent:1em" , ^50mK , colspan=3 style="text-indent:2em" , 171.4(4) keV , 125(40) ns , IT , ⁵⁰K , (2−) , , , - , rowspan=2, ⁵¹K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 32 , rowspan=2, 50.975828(14) , rowspan=2, 365(5) ms , β⁻, n (65%) , ⁵⁰Ca , rowspan=2, 3/2+ , rowspan=2, , rowspan=2, , - , β⁻ (35%) , ⁵¹Ca , - , rowspan=3, ⁵²K , rowspan=3 style="text-align:right" , 19 , rowspan=3 style="text-align:right" , 33 , rowspan=3, 51.98160(4) , rowspan=3, 110(4) ms , β⁻, n (74%) , ⁵¹Ca , rowspan=3, 2−# , rowspan=3, , rowspan=3, , - , β⁻ (23.7%) , ⁵²Ca , - , β⁻, 2n (2.3%) , ⁵⁰Ca , - , 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 , - , rowspan=2, ⁵⁴K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 35 , rowspan=2, 53.99463(64)# , rowspan=2, 10(5) ms , β⁻ (>99.9%) , ⁵⁴Ca , rowspan=2, 2−# , rowspan=2, , rowspan=2, , - , β⁻, n (<.1%) , ⁵³Ca , - , rowspan=2, ⁵⁵K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 36 , rowspan=2, 55.00076(75)# , rowspan=2, 3# ms , β⁻ , ⁵⁵Ca , rowspan=2, 3/2+# , rowspan=2, , rowspan=2, , - , β⁻, n , ⁵⁴Ca , - , rowspan=2, ⁵⁶K , rowspan=2 style="text-align:right" , 19 , rowspan=2 style="text-align:right" , 37 , rowspan=2, 56.00851(86)# , rowspan=2, 1# ms , β⁻ , ⁵⁶Ca , rowspan=2, 2−# , rowspan=2, , rowspan=2, , - , β⁻, n , ⁵⁵Ca , - , ⁵⁷K , style="text-align:right" , 19 , style="text-align:right" , 38 , , , β⁻ , ⁵⁷Ca , , , , - , ⁵⁹KDiscovery of this isotope is unconfirmed , style="text-align:right" , 19 , style="text-align:right" , 40 , , , β⁻ , ⁵⁹Ca , , ,

References

{{Navbox element isotopes Potassium Potassium

List of isotopes

See also

References