Isotopes of chlorine
|Standard atomic weight (Ar, standard)|
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Chlorine (17Cl) has 25 isotopes with mass numbers ranging from 28Cl to 52Cl and 2 isomers (34mCl and 38mCl). There are two principal 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. Bromine is the only other halogen with more than one stable isotope.
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.
List of isotopes
This article needs to be updated.(July 2018)
isotopic mass (u)
|range of natural|
|31Cl||17||14||30.99241(5)||150(25) ms||β+ (99.3%)||31S||3/2+|
|β+, p (.7%)||30P|
|32Cl||17||15||31.985690(7)||298(1) ms||β+ (99.92%)||32S||1+|
|β+, α (.054%)||28Si|
|β+, p (.026%)||31P|
|34mCl||146.36(3) keV||32.00(4) min||β+ (55.4%)||34S||3+|
|36Cl[n 3]||17||19||35.96830698(8)||3.01(2)×105 y||β− (98.1%)||36Ar||2+||Trace[n 4]||approx. 7×10−13|
|38mCl||671.361(8) keV||715(3) ms||IT||38Cl||5−|
|43Cl||17||26||42.97405(17)||3.07(7) s||β− (>99.9%)||43Ar||3/2+#|
|β−, n (<.1%)||42Ar|
|44Cl||17||27||43.97828(12)||0.56(11) s||β− (92%)||44Ar|
|β−, n (8%)||43Ar|
|45Cl||17||28||44.98029(13)||400(40) ms||β− (76%)||45Ar||3/2+#|
|β−, n (24%)||44Ar|
|46Cl||17||29||45.98421(77)||232(2) ms||β−, n (60%)||45Ar|
|47Cl||17||30||46.98871(64)#||101(6) ms||β− (97%)||47Ar||3/2+#|
|β−, n (3%)||46Ar|
|48Cl||17||31||47.99495(75)#||100# ms [>200 ns]||β−||48Ar|
|49Cl||17||32||49.00032(86)#||50# ms [>200 ns]||β−||49Ar||3/2+#|
|51Cl||17||34||51.01449(107)#||2# ms [>200 ns]||β−||51Ar||3/2+#|
- 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.
- Isotope masses from:
- Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
- Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in:
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
- Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- "Universal Nuclide Chart". nucleonica. (Registration required (help)).