Chlorine-37
Properties and data of the isotope 37Cl.
Chlorine-37 is a naturally occurring, stable isotope of the chemical element chlorine, which has 20 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 37.
The first identification and thus discovery of chlorine-35 as an isotopic component of natural chlorine was reported in 1919 [1].
See also: List of individual Chlorine isotopes (and general data sources).
General data
Name of the isotope:Chlorine-37; Cl-37Symbol:37Cl or 3717ClMass number A:37 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:20Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.1764705882353 (= neutron-proton ratio)Neutron excess (N-Z):3Isotopic mass:36.96590257(6) u (atomic weight of Chlorine-37)Nuclide mass:36.9565768 u (calculated nuclear mass without electrons)Mass excess:-31.76155 MeVMass defect:0.340421294 u (per nucleus)Nuclear binding energy:317.10039283 MeV (per nucleus)
8.57028089 MeV (average binding energy per nucleon)Separation energy:SN = 10.31086(6) MeV (first neutron)
SP = 8.38638(19) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)3/2+Magnetic dipole moment:μ(μN) = +0.68400(1)Charge radius:3.3840(170) femtometer fmMirror nucleus:Calcium-37Year of discovery:1919
Parent Nuclides
Direct parent isotopes are: 37Ar, 37S.
Occurrence
Comparison of the natural Chlorine isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
| | Atomic Mass ma | Quantity | Half-life | Spin |
|---|
Chlorine
Isotopic mixture | 35.45 u | 100 % | | |
| Isotope 35Cl | 34.9688527(3) u | 75.80(17) %
[75.5 - 76.1 %] | stable | 3/2+ |
| Isotope 36Cl | 35.96830682(4) u |
[trace] | 3.013(15) × 105 a | 2+ |
| Isotope 37Cl | 36.96590257(6) u | 24.2 %
[23.9 - 24.5 %] | stable | 3/2+ |
NMR data
Nuclear magnetic properties and parameters of the NMR active Nuclide 37Cl
Isotope:37Cl-NMRQuantity:24.2 % [23.9 - 24.5 %]Spin:3/2+Nuclearmagnetic moment
μ/μN:+0.68400(1)Gyromagnetic ratio γ:2.1842 · 107 rad T-1 s-1
3.47626 MHz T-1Nuclear g-factor:gl = 0.456Quadrupole moment Q:- 0.06393 barn (100 fm2)Resonance frequency:v0 = 3.4765 MHz at 1 TRelative Sensitivity:[related to 1H = 1.000]:
0.00272 (H0 = const.)
0.4083 (v0 = const.)
0.000659 (at natural abundance)
relative receptivity as compared to 13C:
3.87 (at natural abundance)Reference compound:
(conditions)sodium chloride solution with 0.1 M NaCl in deuterium oxide D2O.Frequency ratio:Ξ(37Cl) = 8.155725 % [based on the reference substance]
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 20) and isobaric (same nucleon number A = 37) with Chlorine-37. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 20 | Isobar A = 37 |
|---|
| 8 | 28O | |
| 9 | 29F | |
| 10 | 30Ne | |
| 11 | 31Na | 37Na |
| 12 | 32Mg | 37Mg |
| 13 | 33Al | 37Al |
| 14 | 34Si | 37Si |
| 15 | 35P | 37P |
| 16 | 36S | 37S |
| 17 | 37Cl | 37Cl |
| 18 | 38Ar | 37Ar |
| 19 | 39K | 37K |
| 20 | 40Ca | 37Ca |
| 21 | 41Sc | 37Sc |
| 22 | 42Ti | |
| 23 | 43V | |
| 24 | 44Cr | |
| 25 | 45Mn | |
| 26 | 46Fe | |
| 27 | 47Co | |
| 28 | 48Ni | |
External data and identifiers
Literature and References
[1] - F. W. Aston:
The Constitution of the Elements.
In: Nature, 104, 393, (1919), DOI 10.1038/104393b0.
Last update: 2026-01-02
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