鉀 原子質量單位 ：39.0983(1)）共有28個同位素 ，其中有2個是穩定 的。
符號 Z N 同位素質量（u ）[ n 1] [ n 2] 半衰期 [ n 1] [ n 2] [ n 3] 衰變 [ 2] 衰變 [ n 4] [ n 5] 原子核 自旋 [ n 1] 相對豐度 莫耳 分率）[ 3] [ n 2] 激發能量[ n 2] 31 K[ 4] [ 5] 19 12 <10 ps 3p 28 S34 K[ 6] 19 15 33.998404(18) p 33 Ar35 K19 16 34.988010(21) 178(8) ms β+ (99.63%)35 Ar3/2+ β+ , p (.37%) 34 Cl36 K19 17 35.981292(8) 342(2) ms β+ (99.94%) 36 Ar2+ β+ , p (.048%) 35 Clβ+ ,α (.012%) 32 S37 K19 18 36.97337589(10) 1.226(7) s β+ 37 Ar3/2+ 38 K19 19 37.9690812(5) 7.636(18) min β+ 38 Ar3+ 38m1 K130.50(28) keV 924.2(3) ms 0+ 38m2 K3458.0(2) keV 21.98(11) µs (7+),(5+) 39 K19 20 38.96370668(20) 稳定 3/2+ 0.932581(44) 40 K[ n 6] [ n 7] 19 21 39.96399848(21) 1.248(3)×109 y β− (89.28%)40 Ca4 1.17(1)×10−4 EC (10.72%)40 Arβ+ (0.001%)[ 7] 40m K1643.639(11) keV 336(12) ns 0+ 41 K19 22 40.96182576(21) 穩定 3/2+ 0.067302(44) 42 K19 23 41.96240281(24) 12.360(12) h β− 42 Ca2 43 K19 24 42.960716(10) 22.3(1) h β− 43 Ca3/2+ 44 K19 25 43.96156(4) 22.13(19) min β− 44 Ca2− 45 K19 26 44.960699(11) 17.3(6) min β− 45 Ca3/2+ 46 K19 27 45.961977(17) 105(10) s β− 46 Ca2(−) 47 K19 28 46.961678(9) 17.50(24) s β− 47 Ca1/2+ 48 K19 29 47.965514(26) 6.8(2) s β− (98.86%) 48 Ca(2−) β− ,n (1.14%) 47 Ca49 K19 30 48.96745(8) 1.26(5) s β− , n (86%) 48 Ca(3/2+) β− (14%) 49 Ca50 K19 31 49.97278(30) 472(4) ms β− (71%) 50 Ca(0−,1,2−) β− , n (29%) 49 Ca51 K19 32 50.97638(54)# 365(5) ms β− (53%) 51 Ca3/2+# β− , n (47%) 50 Ca52 K19 33 51.98261(75)# 105(5) ms β− , n (64%) 51 Ca(2−)# β− , 2n (21%) 50 Caβ− (15%) 52 Ca53 K19 34 52.98712(75)# 30(5) ms β− , n (67%) 52 Ca(3/2+)# β− , 2n (17%) 51 Caβ− (16%) 53 Ca54 K19 35 53.99420(97)# 10(5) ms β− (>99.9%) 54 Ca2−# β− , n (<.1%) 53 Ca55 K19 36 54.99971(107)# 3# ms β− 55 Ca3/2+# β− , n 54 Ca56 K19 37 56.00851(86)# 1# ms β− 56 Ca2−# β− , n 55 Ca57 K[ 8] [ 9] 19 38 β− 57 Ca59 K[ 9] [ n 8] 19 40 β− 59 Ca
^1.0 1.1 1.2 畫上#號的數據代表沒有經過實驗的証明，僅為理論推測。 ^2.0 2.1 2.2 2.3 用括號括起來的數據代表不確定性。 ^ 半衰期超过5亿年的同位素以粗體 表示。 ^ 穩定 的衰變產物以粗體 表示。^ 半衰期超过5亿年的衰变产物以粗斜体 ^ 用于鉀－氬年代測定法 ^ 原始 （ 英语 ： Primordial nuclide ） 放射性核素 ^ 未确认的同位素 ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J.Standard atomic weights of the elements 2021 (IUPAC Technical Report) . Pure and Applied Chemistry. 2022-05-04.ISSN 1365-3075 doi:10.1515/pac-2019-0603 （英语） . ^ Universal Nuclide Chart [2012-08-15 ] . （原始内容存档 于2017-02-19）. 含有內容需登入查看的頁面 (link ) ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G.The NUBASE2020 evaluation of nuclear properties (PDF) . Chinese Physics C. 2021,45 (3): 030001.doi:10.1088/1674-1137/abddae （英语） . ^ A peculiar atom shakes up assumptions of nuclear structure. Nature. 6 September 2019,573 (7773): 167.Bibcode:2019Natur.573T.167. PMID 31506620 doi:10.1038/d41586-019-02655-9 ^ Kostyleva, D.; et al. Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope31 K by Measuring Its Three-Proton Decay. Physical Review Letters. 2019,123 (9): 092502.Bibcode:2019PhRvL.123i2502K PMID 31524489 S2CID 159041565 arXiv:1905.08154 doi:10.1103/PhysRevLett.123.092502 ^ Dronchi, N.; Charity, R. J.; Sobotka, L. G.; Brown, B. A.; Weisshaar, D.; Gade, A.; Brown, K. W.; Reviol, W.; Bazin, D.; Farris, P. J.; Hill, A. M.; Li, J.; Longfellow, B.; Rhodes, D.; Paneru, S. N.; Gillespie, S. A.; Anthony, A. K.; Rubino, E.; Biswas, S. Evolution of shell gaps in the neutron-poor calcium region from invariant-mass spectroscopy of37,38 Sc,35 Ca, and34 K. Physical Review C. 2024-09-12,110 (3).ISSN 2469-9985 doi:10.1103/PhysRevC.110.L031302 ^ Engelkemeir, D. W.; Flynn, K. F.; Glendenin, L. E.Positron Emission in the Decay of K40 . Physical Review. 1962,126 (5): 1818 [2015-09-11 ] .Bibcode:1962PhRv..126.1818E doi:10.1103/PhysRev.126.1818 存档 于2019-07-01）. ^ Neufcourt, L.; Cao, Y.; Nazarewicz, W.; Olsen, E.; Viens, F. Neutron drip line in the Ca region from Bayesian model averaging. Physical Review Letters. 2019,122 (6): 062502–1–062502–6.Bibcode:2019PhRvL.122f2502N PMID 30822058 S2CID 73508148 arXiv:1901.07632 doi:10.1103/PhysRevLett.122.062502 ^9.0 9.1 Tarasov, O.B.Production of very neutron rich isotopes: What should we know? . 2017 [2023-05-21 ] . （原始内容存档 于2022-02-02）. Isotope masses fromAme2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon inNuclear Physics A729 (2003). Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.Audi, Bersillon, Blachot, Wapstra.The Nubase2003 evaluation of nuclear and decay properties （页面存档备份 ，存于互联网档案馆 ）, Nuc. Phys. A 729, pp. 3-128 (2003). National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from theNuDat 2.1 database （页面存档备份 ，存于互联网档案馆 ） (retrieved Sept. 2005). David R. Lide (ed.), Norman E. Holden inCRC Handbook of Chemistry and Physics, 85th Edition , online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
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