1. Chlorine-36 (³⁶Cl)

2. Chlorine-37

3. List of isotopes
     Notes  

4. References

5. External links

Chlorine (₁₇Cl) has 25 isotopes with mass numbers ranging from ²⁸Cl to ⁵²Cl and 2 isomers (^34mCl and ^38mCl). There are two stable isotopes, ³⁵Cl (75.78%) and ³⁷Cl (24.22%), giving chlorine a standard atomic weight of 35.45. The longest-lived radioactive isotope is ³⁶Cl, which has a half-life of 301,000 years. All other isotopes have half-lives under 1 hour, many less than one second. The shortest-lived are ²⁹Cl and ³⁰Cl, with half-lives less than 20 and 30 nanoseconds, respectively—the half-life of ²⁸Cl is unknown.

Chlorine-36 (³⁶Cl)

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 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.

Chlorine-37

List of isotopes

Notes

• Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
• Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

• Isotope masses from:
  • {{cite journal |author=G. Audi |author2=A. H. Wapstra |author3=C. Thibault |author4=J. Blachot |author5=O. Bersillon |year=2003 |title=The NUBASE evaluation of nuclear and decay properties |url=http://amdc.in2p3.fr/nubase/Nubase2003.pdf |journal=Nuclear Physics A |volume=729 |issue= 1|pages=3–128 |doi=10.1016/j.nuclphysa.2003.11.001 |bibcode=2003NuPhA.729....3A |deadurl=yes |archiveurl=https://web.archive.org/web/20110720233206/http://amdc.in2p3.fr/nubase/Nubase2003.pdf |archivedate=2011-07-20 |df= |citeseerx=10.1.1.692.8504 }}
• Isotopic compositions and standard atomic masses from:
  • {{CAWIA 2003}}
  • {{CIAAW 2005}}
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • {{NUBASE 2003}}
  • {{NNDC}}
  • {{CRC85|chapter=11}}

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