Chlorine-42

Properties and data of the isotope ⁴²Cl.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Chlorine-42 is a radioisotope of the chemical element chlorine, which has 25 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 42. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁴²Cl is exclusively for academic purposes.

The radioactive isotope was first described in 1971; according to this, chlorine-42 was formed as a fission product when a thorium-232 template was irradiated with argon-40 ions of an energy of 290 MeV [1].

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

General data

Name of the isotope:Chlorine-42; Cl-42Symbol:⁴²Cl or 4217ClMass number A:42 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:25Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.4705882352941 (= neutron-proton ratio)Neutron excess (N-Z):8Isotopic mass:41.97334(6) u (atomic weight of Chlorine-42)Nuclide mass:41.9640143 u (calculated nuclear mass without electrons)Mass excess:-24.83363 MeVMass defect:0.376308444 u (per nucleus)Nuclear binding energy:350.52905774 MeV (per nucleus)
8.34592995 MeV (average binding energy per nucleon)Separation energy:S_N = 5.596(91) MeV (first neutron)
S_P = 13.112(60) MeV (first proton)Half-life:6.8(3) sDecay constant λ:0.10193340890587 s^-1Specific activity α:1.497213040889 × 10⁺²¹ Bq g^-1
40465217321.338 Ci g^-1Spin and parity:
(nuclear angular momentum)(2-)Mirror nucleus:Manganese-42Year of discovery:1971

Radioactive Decay

Half-life T_½ = 6.8(3) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁴²Ar	100 %	9.59(6) MeV

Parent Nuclides

Direct parent isotopes are: ⁴²S, ⁴³S.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 25) and isobaric (same nucleon number A = 42) with Chlorine-42. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 25	Isobar A = 42
11	³⁶Na
12	³⁷Mg
13	³⁸Al	⁴²Al
14	³⁹Si	⁴²Si
15	⁴⁰P	⁴²P
16	⁴¹S	⁴²S
17	⁴²Cl	⁴²Cl
18	⁴³Ar	⁴²Ar
19	⁴⁴K	⁴²K
20	⁴⁵Ca	⁴²Ca
21	⁴⁶Sc	⁴²Sc
22	⁴⁷Ti	⁴²Ti
23	⁴⁸V	⁴²V
24	⁴⁹Cr	⁴²Cr
25	⁵⁰Mn	⁴²Mn
26	⁵¹Fe
27	⁵²Co
28	⁵³Ni
29	⁵⁴Cu
30	⁵⁵Zn