Potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...

() has 26 known

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

s 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 Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

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 a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

, 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. ...

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 ...

. has the longest known half life for any positron-emitter

nuclide A nuclide (or nucleide, from atomic nucleus, 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 co ...

. 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 ...

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

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 chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

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 chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by ...

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, and biological organisms. Weathering occurs '' in situ'' (on site, with little or no movement ...

. 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&nbs ...

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 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 excr ...

required for

life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy ...

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 n ...

, 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 t ...

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

List of isotopes

See also

References