Potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

() has 25 known

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

s from to as well as , 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 Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of 1.248×10⁹ years. 89% of those decays are to stable by

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

, whilst 11% are to by either

electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...

positron emission Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron emi ...

. This latter decay branch has produced an isotopic abundance of argon on Earth which differs greatly from that seen in

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...

s and stellar spectra. has the longest known half-life for any positron-emitter

nuclide Nuclides (or nucleides, from nucleus, also known as nuclear species) are 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 the A ...

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

nuclear spin Nuclear may refer to: Physics Relating to the nucleus of the atom: * Nuclear engineering * Nuclear physics * Nuclear power * Nuclear reactor * Nuclear weapon * Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics * Nuclear space * ...

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 sa ...

commercial

salt substitute A salt substitute, also known as low-sodium salt, is a low-sodium alternative to edible salt (table salt) marketed to reduce the risk of high blood pressure and cardiovascular disease associated with a high intake of sodium chloride while maintai ...

s can be used as a

radioactive source A radioactive source is a known quantity of a radionuclide which emits ionizing radiation, typically one or more of the radiation types gamma rays, alpha particles, beta particles, and neutron radiation. Sources can be used for irradiation, where ...

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.

Mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s 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 A radioactive tracer, radiotracer, or radioactive label is a synthetic derivative of a natural compound in which one or more atoms have been replaced by a radionuclide (a radioactive atom). By virtue of its radioactive decay, it can be used to ...

in studies of

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

. 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. Stable potassium isotopes have been used for several

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 cyc ...

studies since potassium is a

macronutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

required for

life Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...

List of isotopes

, -id=Potassium-31 , , style="text-align:right" , 19 , style="text-align:right" , 12 , 31.03678(32)# , <10 ps , 3p , ²⁸S , 3/2+# , , , -id=Potassium-34 , ³⁴K , 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, ⁴⁰KUsed in potassium-argon dating Primordial

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

, 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%) , -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− , TraceDecay product of ⁴²Ar , , -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, 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, 1# ms
400 ns, β⁻? , ⁵⁹Ca , rowspan=3, 3/2+# , rowspan=3, , rowspan=3, , - , β⁻, n? , ⁵⁸Ca , - , β⁻, 2n? , ⁵⁷Ca

References

{{Navbox element isotopes Potassium

List of isotopes

See also

References