Chlorine-40 is a radioisotope of the chemical element chlorine, which has 23 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 40. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of 40Cl is exclusively for academic purposes.
See also: List of individual Chlorine isotopes (and general data sources).
General data
Name of the isotope:Chlorine-40; Cl-40Symbol:40Cl or 4017ClMass number A:40 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:23Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.3529411764706 (= neutron-proton ratio)Neutron excess (N-Z):6Isotopic mass:39.97042(3) u (atomic weight of Chlorine-40)Nuclide mass:39.9610943 u (calculated nuclear mass without electrons)Mass excess:-27.55359 MeVMass defect:0.361898612 u (per nucleus)Nuclear binding energy:337.10638569 MeV (per nucleus) 8.42765964 MeV (average binding energy per nucleon)Separation energy:SN = 5.829(32) MeV (first neutron) SP = 11.684(5) MeV (first proton)Half-life:1.35(3) minDecay constant λ:0.00085573725995055 s-1Specific activity α:1.289295992636 × 10+19 Bq g-1 348458376.38819 Ci g-1Spin and parity: (nuclear angular momentum)2-Mirror nucleus:Vanadium-40Year of discovery:1956
Radioactive Decay
Half-life T½ = 1.35(3) min (minutes) respectively 8.10 × 102 seconds s.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 23) and isobaric (same nucleon number A = 40) with Chlorine-40. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
