Chlorine-38

Properties and data of the isotope ³⁸Cl.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Chlorine-38 is a radioisotope of the chemical element chlorine, which has 21 neutrons in its atomic nucleus in addition to the element-specific 17 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 38. The short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³⁸Cl is exclusively for academic purposes and experimental research.

A report on the discovery of the isotope during the irradiation of chlorine-containing templates with neutrons was published in 1940 [1].

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

General data

Name of the isotope:Chlorine-38; Cl-38Symbol:³⁸Cl or 3817ClMass number A:38 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:21Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.2352941176471 (= neutron-proton ratio)Neutron excess (N-Z):4Isotopic mass:37.96801041(11) u (atomic weight of Chlorine-38)Nuclide mass:37.9586847 u (calculated nuclear mass without electrons)Mass excess:-29.79811 MeVMass defect:0.34697837 u (per nucleus)Nuclear binding energy:323.20826978 MeV (per nucleus)
8.50548078 MeV (average binding energy per nucleon)Separation energy:S_N = 6.10788(8) MeV (first neutron)
S_P = 10.19066(21) MeV (first proton)Half-life:37.230(14) minDecay constant λ:0.00031029957048972 s^-1Specific activity α:5.050453303424 × 10⁺¹⁸ Bq g^-1
136498737.93039 Ci g^-1Spin and parity:
(nuclear angular momentum)2-Magnetic dipole moment:μ(μ_N) = 2.05(2)Nuclear g-factor:g_l = 1.025Mirror nucleus:Scandium-38Year of discovery:1940

Radioactive Decay

Half-life T_½ = 37.230(14) min (minutes) respectively 2.2338 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	³⁸Ar	100 %	4.91671(22) MeV	1.64268(2) MeV [32.9(5) %] 2.167400(9) MeV [44.0(6) %]

Parent Nuclides

Direct parent isotope is: ³⁸S.

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
^38mCl	671.365(8) keV	715(3) ms	5-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 21) and isobaric (same nucleon number A = 38) with Chlorine-38. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 21	Isobar A = 38
9	³⁰F
10	³¹Ne
11	³²Na	³⁸Na
12	³³Mg	³⁸Mg
13	³⁴Al	³⁸Al
14	³⁵Si	³⁸Si
15	³⁶P	³⁸P
16	³⁷S	³⁸S
17	³⁸Cl	³⁸Cl
18	³⁹Ar	³⁸Ar
19	⁴⁰K	³⁸K
20	⁴¹Ca	³⁸Ca
21	⁴²Sc	³⁸Sc
22	⁴³Ti	³⁸Ti
23	⁴⁴V
24	⁴⁵Cr
25	⁴⁶Mn
26	⁴⁷Fe
27	⁴⁸Co
28	⁴⁹Ni