Isotopes of chlorine

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Chlorine (Cl) has 24 isotopes with mass numbers ranging from 28Cl to 51Cl and 2 isomers (34mCl and 38mCl). There are two principal stable isotopes, 35Cl (75.78%) and 37Cl (24.22%), found in the relative proportions of 37.89:12.11, respectively, giving chlorine a standard atomic mass of 35.453. 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.

Standard atomic mass: 35.453(2) u

Chlorine-36 (36Cl)[edit]

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 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.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[1][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
28Cl 17 11 28.02851(54)# p 27S (1+)#
29Cl 17 12 29.01411(21)# <20 ns p 28S (3/2+)#
30Cl 17 13 30.00477(21)# <30 ns p 29S (3+)#
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
33Cl 17 16 32.9774519(5) 2.511(3) s β+ 33S 3/2+
34Cl 17 17 33.97376282(19) 1.5264(14) s β+ 34S 0+
34mCl 146.36(3) keV 32.00(4) min β+ (55.4%) 34S 3+
IT (44.6%) 34Cl
35Cl 17 18 34.96885268(4) Stable 3/2+ 0.7576(10) 0.75644-0.75923
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
ε (1.9%) 36S
37Cl 17 20 36.96590259(5) Stable 3/2+ 0.2424(10) 0.24077-0.24356
38Cl 17 21 37.96801043(10) 37.24(5) min β- 38Ar 2-
38mCl 671.361(8) keV 715(3) ms IT 38Cl 5-
39Cl 17 22 38.9680082(19) 55.6(2) min β- 39Ar 3/2+
40Cl 17 23 39.97042(3) 1.35(2) min β- 40Ar 2-
41Cl 17 24 40.97068(7) 38.4(8) s β- 41Ar (1/2+,3/2+)
42Cl 17 25 41.97325(15) 6.8(3) s β- 42Ar
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
β- (40%) 46Ar
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+#
50Cl 17 33 50.00784(97)# 20# ms β- 50Ar
51Cl 17 34 51.01449(107)# 2# ms [>200 ns] β- 51Ar 3/2+#
  1. ^ Abbreviations:
    IT: Isomeric transition
  2. ^ Bold for stable isotopes
  3. ^ Used in radiodating water
  4. ^ Cosmogenic nuclide

Notes[edit]

  • 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[edit]

  1. ^ http://www.nucleonica.net/unc.aspx

External links[edit]


Isotopes of sulfur Isotopes of chlorine Isotopes of argon
Table of nuclides