Isotopes of potassium

Isotope data
potassium symbol icon

Although Potassium only has two stable isotopes (K-39 and K-41), the long-lived radioisotope K-40 is often also regarded as a stable isotope. Potassium isotopes, mainly K-40 and K-41, are used to study the impact of potassium on the growth of plants and of the human cardiovascular system. Potassium isotopes, including K-40, can be obtained from Trace Sciences International.

Naturally occurring isotopes

This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances, their nuclear spins, and their magnetic moments. Further data for radioisotopes (radioactive isotopes) of potassium are listed (including any which occur naturally) below.
Isotope Atomic mass (ma/u) Natural abundance (atom %) Nuclear spin (I) Magnetic moment (μ/μN)
39K 38.9637074 (12) 93.2581 (44) 3/2 0.3914658
40K 39.9639992 (12) 0.0117 (1) 4 -1.298099
41K 40.9618254 (12) 6.7302 (44) 3/2 0.2148699

Isotopic abundances of K
In the above picture, the most intense ion is set to 100% since this corresponds best to the output from a mass spectrometer. This is not to be confused with the relative percentage isotope abundances which total 100% for all the naturally occurring isotopes.

Radiosotope data

Further data for naturally occuring isotopes of potassium are listed above. This table gives information about some radiosotopes of potassium, their masses, their half-lives, their modes of decay, their nuclear spins, and their nuclear magnetic moments.
Isotope Mass Half-life Mode of decay Nuclear spin Nuclear magnetic moment
37K 36.9733769 EC to 37Ar 3/2 0.2032
38K 37.969080 7.63 m EC to 38Ar 3 1.37
40K 39.9639987 1.277 x 109 y EC to 40Ar 4
42K 41.9624031 12.36 h β- to 42Ca 2 -1.1425
43K 42.96072 22.3 h β- to 43Ca 3/2 0.163
44K 43.96156 22.1 m β- to 44Ca 2 -0.856
45K 44.96070 17.8 m β- to 45Ca 3/2 0.1734
46K 45.96168 1.8 m β- to 46Ca 2 -1.05
47K 46.96551 17.5 s β- to 47Ca 1/2 1.93
48K 47.96551 6.8 s β- to 48Ca; β- + n to 47Ca 2
49K 48.96745 1.26 s β- to 49Ca; β- + n to 48Ca

Sheffield ChemPuter isotope pattern calculator

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References

  1. Naturally occurring isotope abundances: Commission on Atomic Weights and Isotopic Abundances report for the International Union of Pure and Applied Chemistry in Isotopic Compositions of the Elements 1989, Pure and Applied Chemistry, 1998, 70, 217. [Copyright 1998 IUPAC]
  2. Masses, nuclear spins, and magnetic moments: I. Mills, T. Cvitas, K. Homann, N. Kallay, and K. Kuchitsu in Quantities, Units and Symbols in Physical Chemistry, Blackwell Scientific Publications, Oxford, UK, 1988. [Copyright 1988 IUPAC]
  3. For further information about radioisotopes see Jonghwa Chang's (Korea Atomic Energy Research Institute) Table of the Nuclides

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potassium atomic number