Potassium-57

Properties and data of the isotope ⁵⁷K.

Contents

Potassium-57 is a radioisotope of the chemical element potassium, which has 38 neutrons in its atomic nucleus in addition to the element-specific 19 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 57. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁵⁷K is exclusively for academic purposes.

The discovery of the neutron-rich isotope was reported in 2018. According to this report, potassium-57 was produced by the fragmentation of a 345 MeV/u beam of zinc-70 ions on a template of beryllium-9; the fragments produced were analyzed and unambiguously identified using the two-stage in-flight separator BigRIPS [1].

See also: List of individual Potassium isotopes (and general data sources).

General data

Name of the isotope:Potassium-57; K-57Symbol:⁵⁷K or 5719KMass number A:57 (= number of nucleons)Atomic number Z:19 (= number of protons)Neutrons N:38Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):2 (= neutron-proton ratio)Neutron excess (N-Z):19Isotopic mass:57.01517(64) u (atomic weight of Potassium-57)Nuclide mass:57.0047472 u (calculated nuclear mass without electrons)Mass excess:14.13076 MeVMass defect:0.462772416 u (per nucleus)Nuclear binding energy:431.06972887 MeV (per nucleus)
7.56262682 MeV (average binding energy per nucleon)Separation energy:S_N = 1.922(848) MeV (first neutron)Half-life:2 msDecay constant λ:346.57359027997 s^-1Specific activity α:3.6606309239533 × 10⁺²⁴ Bq g^-1
98935970917657 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2+)Year of discovery:2018

Radioactive Decay

Half-life T_½ = 2 ms respectively 2 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁵⁷Ca	100 %	20.69(72) MeV
β^-, xn ?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 38) and isobaric (same nucleon number A = 57) with Potassium-57. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 38	Isobar A = 57
19	⁵⁷K	⁵⁷K
20	⁵⁸Ca	⁵⁷Ca
21	⁵⁹Sc	⁵⁷Sc
22	⁶⁰Ti	⁵⁷Ti
23	⁶¹V	⁵⁷V
24	⁶²Cr	⁵⁷Cr
25	⁶³Mn	⁵⁷Mn
26	⁶⁴Fe	⁵⁷Fe
27	⁶⁵Co	⁵⁷Co
28	⁶⁶Ni	⁵⁷Ni
29	⁶⁷Cu	⁵⁷Cu
30	⁶⁸Zn	⁵⁷Zn
31	⁶⁹Ga
32	⁷⁰Ge
33	⁷¹As
34	⁷²Se
35	⁷³Br
36	⁷⁴Kr
37	⁷⁵Rb
38	⁷⁶Sr
39	⁷⁷Y
40	⁷⁸Zr

External data and identifiers

Adopted Levels, Gammas:NuDat 57K

Literature and References

[1] - O. B. Tarasov, D. S. Ahn, D. Bazin et al.:
Discovery of ⁶⁰Ca and Implications For the Stability of ⁷⁰Ca.
In: Physical Review Letters, 121, 022501, (2018), DOI 10.1103/PhysRevLett.121.022501.