Isotopes of chlorine

Isotopes of chlorine (17Cl)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
35Cl 75.8% stable
36Cl trace 3.01×105 y β− 36Ar
ε 36S
37Cl 24.2% stable
Standard atomic weight Ar°(Cl)

Chlorine (17Cl) has two stable isotopes, 35Cl (75.8%) and 37Cl (24.2%), giving chlorine a standard atomic weight of 35.45. Artificical radioisotopes are known ranging from 28Cl to 52Cl, and there are also two isomers, 34mCl and 38mCl. The longest-lived radioactive isotope is 36Cl, which has a half-life of 301,000 years. All other isotopes and isomers have half-lives under an hour, and most under 10 seconds.

List of isotopes

Nuclide
[n 1] 		Z N Isotopic mass (Da)[4]
[n 2][n 3] 		Half-life[1]
[n 4] 		Decay
mode[1]
[n 5] 		Daughter
isotope
[n 6] 		Spin and
parity[1]
[n 7][n 4] 		Natural abundance (mole fraction)
Excitation energy Normal proportion[1] Range of variation
28Cl[5] 17 11 28.03035(54)# p 27S 1+#
29Cl 17 12 29.01505(20)# 5.4(19) zs p 28S (1/2+)
30Cl 17 13 30.005018(26) <50 ns[5] p 29S 3+#
31Cl 17 14 30.9924481(37) 190(1) ms β+ (97.6%) 31S 3/2+
β+, p (2.4%) 30P
32Cl 17 15 31.98568461(60) 298(1) ms β+ (99.92%) 32S 1+
β+, α (0.054%) 28Si
β+, p (0.026%) 31P
33Cl 17 16 32.97745199(42) 2.5038(22) s β+ 33S 3/2+
34Cl 17 17 33.973762490(52) 1.5267(4) s β+ 34S 0+
34mCl 146.360(27) keV 31.99(3) min β+ (55.4%) 34S 3+
IT (44.6%) 34Cl
35Cl 17 18 34.968852694(38) Stable 3/2+ 0.758(2)
36Cl[n 8] 17 19 35.968306822(38) 3.013(15)×105 y β− (98.1%) 36Ar 2+ 7×10−13[6][7][n 9]
β+ (1.9%) 36S
37Cl 17 20 36.965902573(55) Stable 3/2+ 0.242(2)
38Cl 17 21 37.96801041(11) 37.230(14) min β− 38Ar 2−
38mCl 671.365(8) keV 715(3) ms IT 38Cl 5−
39Cl 17 22 38.9680082(19) 56.2(6) min β− 39Ar 3/2+
40Cl 17 23 39.970415(34) 1.35(3) min β− 40Ar 2−
41Cl 17 24 40.970685(74) 38.4(8) s β− 41Ar (1/2+)
42Cl 17 25 41.973342(64) 6.8(3) s β− 42Ar (2−)
β−, n? 41Ar
43Cl 17 26 42.974064(66) 3.13(9) s β− 43Ar (3/2+)
β−, n? 42Ar
44Cl 17 27 43.978015(92) 0.56(11) s β− (>92%) 44Ar (2-)
β−, n? (<8%) 43Ar
45Cl 17 28 44.98039(15) 513(36) ms[8] β− (76%) 45Ar (3/2+)
β−, n (24%) 44Ar
46Cl 17 29 45.98525(10) 232(2) ms β−, n (60%) 45Ar 2-#
β− (40%) 46Ar
β−, 2n? 44Ar
47Cl 17 30 46.98972(22)# 101(5) ms β− (>97%) 47Ar 3/2+#
β−, n? (<3%) 46Ar
β−, 2n? 45Ar
48Cl 17 31 47.99541(54)# 30# ms
[>200 ns] 		β−? 48Ar
β−, n? 47Ar
β−, 2n? 46Ar
49Cl 17 32 49.00079(43)# 35# ms
[>200 ns] 		β−? 49Ar 3/2+#
β−, n? 48Ar
β−, 2n? 47Ar
50Cl 17 33 50.00827(43)# 10# ms
[>620 ns] 		β− 50Ar
β−, n? 49Ar
β−, 2n? 48Ar
51Cl 17 34 51.01534(75)# 5# ms
[>200 ns] 		β−? 51Ar 3/2+#
β−, n? 50Ar
β−, 2n? 49Ar
52Cl 17 35 52.02400(75)# 2# ms
[>400 ns] 		β−? 52Ar
β−, n? 51Ar
β−, 2n? 50Ar
This table header & footer:
  1. ^ mCl – Excited nuclear isomer.
  2. ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ^ Modes of decay:
    IT: Isomeric transition
    n: Neutron emission
    p: Proton emission
  6. ^ Bold symbol as daughter – Daughter product is stable.
  7. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  8. ^ Used in radiodating water
  9. ^ Cosmogenic nuclide

Stable isotope analysis

The representative terrestrial abundance of chlorine contains about is 24.2% of 37Cl, with a normal range of 23.9–24.5% of chlorine atoms.[2] When measuring deviations in isotopic composition, the usual reference point is "Standard Mean Ocean Chloride" (SMOC), although a NIST Standard Reference Material (975a) also exists. SMOC is known to have a 37Cl/35Cl ratio of 0.319627 ± 0.000199 (24.221% +/- 0.0015% chlorine-37)[9] and to have an atomic weight of 35.4525.

There is known variation in the isotopic abundance of chlorine. This heavier isotope tends to be more prevalent in chloride minerals than in aqueous solutions such as seawater, although the isotopic composition of organochlorine compounds can vary in either direction from the SMOC standard in the range of several parts per thousand.[2]

Chlorine-36

Main article: Chlorine-36

Trace amounts of radioactive 36Cl exist in the environment, in a ratio of about 7×10−13 to 1 with stable isotopes. 36Cl is produced in the atmosphere by spallation of 36Ar by interactions with cosmic ray protons. In the subsurface environment, 36Cl is generated primarily as a result of neutron capture by 35Cl or muon capture by 40Ca. 36Cl decays to either 36S (1.9%) or to 36Ar (98.1%), with a combined half-life of 308,000 years. The half-life of this hydrophilic nonreactive isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years. Additionally, large amounts of 36Cl were produced by neutron irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958. The residence time of 36Cl in the atmosphere is about 1 week. Thus, as an event marker of 1950s water in soil and ground water, 36Cl is also useful for dating waters less than 50 years before the present. 36Cl has seen use in other areas of the geological sciences, forecasts, and elements. In chloride-based molten salt reactors the production of 36
Cl by neutron capture is an inevitable consequence of using natural isotope mixtures of chlorine (i.e. Those containing 35
Cl). This produces a long lived radioactive product which has to be stored or disposed off. Isotope separation to produce pure 37
Cl can vastly reduce 36
Cl production, but a small amount might still be produced by (n,2n) reactions involving fast neutrons.

Chlorine-37

Main article: Chlorine-37

Besides being a component of natural stable chlorine, the chief notability of this isotope is its use to detect solar neutrinos through inverse electron capture (producing the gas 37Ar). This was used in the first detection at the Homestake experiment. Subsequently gallium-71 was found more suitable for this purpose, and used in GALLEX/GNO and SAGE.

See also

Daughter products other than chlorine

References

  1. ^ a b c d e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.
  2. ^ a b c "Standard Atomic Weights: Chlorine". CIAAW. 2009.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
  5. ^ a b Mukha, I.; et al. (2018). "Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains". Physical Review C. 98 (6): 064308–1–064308–13. arXiv:1803.10951. Bibcode:2018PhRvC..98f4308M. doi:10.1103/PhysRevC.98.064308. S2CID 119384311.
  6. ^ M. Zreda; et al. (1991). "Cosmogenic chlorine-36 production rates in terrestrial rocks". Earth and Planetary Science Letters. 105 (1–3): 94–109. Bibcode:1991E&PSL.105...94Z. doi:10.1016/0012-821X(91)90123-Y.
  7. ^ M. Sheppard and M. Herod (2012). "Variation in background concentrations and specific activities of 36Cl, 129I and U/Th-series radionuclides in surface waters". Journal of Environmental Radioactivity. 106: 27–34. doi:10.1016/j.jenvrad.2011.10.015. PMID 22304997.
  8. ^ Bhattacharya, Soumik; Tripathi, Vandana; Tabor, S. L.; Volya, A.; Bender, P. C.; Benetti, C.; Carpenter, M. P.; Carroll, J. J.; Chester, A.; Chiara, C. J.; Childers, K.; Clark, B. R.; Crider, B. P.; Harke, J. T.; Jain, R.; Liddick, S. N.; Lubna, R. S.; Luitel, S.; Longfellow, B.; Mogannam, M. J.; Ogunbeku, T. H.; Perello, J.; Richard, A. L.; Rubino, E.; Saha, S.; Shehu, O. A.; Unz, R.; Xiao, Y.; Zhu, Yiyi (2023-08-18). "β− decay of neutron-rich 45Cl located at the magic number N=28" (PDF). Physical Review C. 108 (2). American Physical Society (APS): 024312. doi:10.1103/physrevc.108.024312. ISSN 2469-9985.{{cite journal}}: CS1 maint: article number as page number (link)
  9. ^ Chlorine-bearing species and the 37Cl/35Cl isotope ratio ... - Figure 8. This is the only source I find giving the actual composition of SMOC (as the isotope ratio). There surely should be a better one.
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