Potassium-42

Properties and data of the isotope ⁴²K.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Potassium-42 is a radioisotope of the chemical element potassium, which has 23 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 42.

A report on the discovery of the radioactive isotope appeared in 1935 [1]: According to this, potassium-42 was produced and identified by irradiating Scandium oxide (containing scandium-45; isotopic composition: see there) with neutrons:

⁴⁵Sc(n,α)⁴²K.

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

General data

Name of the isotope:Potassium-42; K-42Other names:RadiokaliumSymbol:⁴²K or 4219KMass number A:42 (= number of nucleons)Atomic number Z:19 (= number of protons)Neutrons N:23Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.2105263157895 (= neutron-proton ratio)Neutron excess (N-Z):4Isotopic mass:41.96240231(11) u (atomic weight of Potassium-42)Nuclide mass:41.9519795 u (calculated nuclear mass without electrons)Mass excess:-35.02202 MeVMass defect:0.385566366 u (per nucleus)Nuclear binding energy:359.15275653 MeV (per nucleus)
8.55125611 MeV (average binding energy per nucleon)Separation energy:S_N = 7.53380(11) MeV (first neutron)
S_P = 9.2435(4) MeV (first proton)Half-life:12.355(7) hDecay constant λ:1.558404560816 × 10^-5 s^-1Specific activity α:2.289007751708 × 10⁺¹⁷ Bq g^-1
6186507.4370497 Ci g^-1Spin and parity:
(nuclear angular momentum)2-Magnetic dipole moment:μ(μ_N) = - 1.1425(6)Nuclear g-factor:g_l = -0.57125Charge radius:3.4517(70) femtometer fmMirror nucleus:Vanadium-42Year of discovery:1935

Radioactive Decay

Half-life T_½ = 12.355(7) h (hours) respectively 4.4478 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁴²Ca	100 %	3.52526(18) MeV

Parent Nuclides

Direct parent isotope is: ⁴²Ar.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 23) and isobaric (same nucleon number A = 42) with Potassium-42. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 23	Isobar A = 42
10	³³Ne
11	³⁴Na
12	³⁵Mg
13	³⁶Al	⁴²Al
14	³⁷Si	⁴²Si
15	³⁸P	⁴²P
16	³⁹S	⁴²S
17	⁴⁰Cl	⁴²Cl
18	⁴¹Ar	⁴²Ar
19	⁴²K	⁴²K
20	⁴³Ca	⁴²Ca
21	⁴⁴Sc	⁴²Sc
22	⁴⁵Ti	⁴²Ti
23	⁴⁶V	⁴²V
24	⁴⁷Cr	⁴²Cr
25	⁴⁸Mn	⁴²Mn
26	⁴⁹Fe
27	⁵⁰Co
28	⁵¹Ni