Potassium-38

Properties and data of the isotope ³⁸K.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Potassium-38 is a radioisotope of the chemical element potassium, which has 19 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 38.

A report on the discovery of the radioactive isotope appeared in 1937; according to this, potassium-38 could be produced and identified by irradiating lithium chloride respectively the chlorine-35 contained therein with alpha particles (helium-4 nuclei) of an energy of 11 MeV [1]:

³⁵Cl(α,n)³⁸K.

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

General data

Name of the isotope:Potassium-38; K-38Symbol:³⁸K or 3819KMass number A:38 (= number of nucleons)Atomic number Z:19 (= number of protons)Neutrons N:19Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1 (= neutron-proton ratio)Neutron excess (N-Z):0Isotopic mass:37.96908111(21) u (atomic weight of Potassium-38)Nuclide mass:37.9586583 u (calculated nuclear mass without electrons)Mass excess:-28.80076 MeVMass defect:0.344227902 u (per nucleus)Nuclear binding energy:320.64622535 MeV (per nucleus)
8.43805856 MeV (average binding energy per nucleon)Separation energy:S_N = 12.07188(22) MeV (first neutron)
S_P = 5.14205(28) MeV (first proton)Half-life:7.651(19) minDecay constant λ:0.0015099272002787 s^-1Specific activity α:2.457566023872 × 10⁺¹⁹ Bq g^-1
664207033.47905 Ci g^-1Spin and parity:
(nuclear angular momentum)3+Isobaric spin: 0Magnetic dipole moment:μ(μ_N) = + 1.371(6)Nuclear g-factor:g_l = 0.457Charge radius:3.4264(51) femtometer fmYear of discovery:1937

Radioactive Decay

Half-life T_½ = 7.651(19) min (minutes) respectively 4.5906 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	Details	γ energy (intensity)
EC/β⁺	³⁸Ar	100 %	5.91407(28) MeV	β⁺: 1.21203(2) MeV [99.332(11) %] annihilation: 0.5110 MeV [199.07(11) %]	2.1675(3) MeV [99.840(10) %]

Parent Nuclides

Direct parent isotope is: ³⁸Ca.

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^38m1K	130.15(4) keV	924.4(3) ms	0+
^38m2K	3458.10(17) keV	21.95(11) μs	(7)+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 19) and isobaric (same nucleon number A = 38) with Potassium-38. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 19	Isobar A = 38
8	²⁷O
9	²⁸F
10	²⁹Ne
11	³⁰Na	³⁸Na
12	³¹Mg	³⁸Mg
13	³²Al	³⁸Al
14	³³Si	³⁸Si
15	³⁴P	³⁸P
16	³⁵S	³⁸S
17	³⁶Cl	³⁸Cl
18	³⁷Ar	³⁸Ar
19	³⁸K	³⁸K
20	³⁹Ca	³⁸Ca
21	⁴⁰Sc	³⁸Sc
22	⁴¹Ti	³⁸Ti
23	⁴²V
24	⁴³Cr
25	⁴⁴Mn
26	⁴⁵Fe
27	⁴⁶Co