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Standard atomic weight Ar°(Cl) | ||||||||||||||||||||||||||||
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Chlorine (17Cl) has 25 isotopes, ranging from 28Cl to 52Cl, and two isomers, 34mCl and 38mCl. There are two stable isotopes, 35Cl (75.8%) and 37Cl (24.2%), 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 proton-unbound 29Cl and 30Cl, with half-lives less than 10 picoseconds and 30 nanoseconds, respectively; the half-life of 28Cl is unknown.
Nuclide
[4] [n 1] |
Z | N |
Isotopic mass (
Da)
[5] [n 2] [n 3] |
Half-life [n 4] |
Decay mode [n 5] |
Daughter isotope [n 6] |
Spin and parity [n 7] [n 4] |
Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion | Range of variation | |||||||||||||||||
28Cl [6] | 17 | 11 | 28.02954(64)# | p | 27S | 1+# | |||||||||||||
29Cl [6] | 17 | 12 | 29.01413(20) | <10 ps | p | 28S | (1/2+) | ||||||||||||
30Cl [6] | 17 | 13 | 30.00477(21)# | <30 ns | p | 29S | 3+# | ||||||||||||
31Cl | 17 | 14 | 30.992448(4) | 190(1) ms | β+ (97.6%) | 31S | 3/2+ | ||||||||||||
β+, p (2.4%) | 30P | ||||||||||||||||||
32Cl | 17 | 15 | 31.9856846(6) | 298(1) ms | β+ (99.92%) | 32S | 1+ | ||||||||||||
β+, α (.054%) | 28Si | ||||||||||||||||||
β+, p (.026%) | 31P | ||||||||||||||||||
33Cl | 17 | 16 | 32.9774520(4) | 2.5038(22) s | β+ | 33S | 3/2+ | ||||||||||||
34Cl | 17 | 17 | 33.97376249(5) | 1.5266(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 | 34.96885269(4) | Stable | 3/2+ | 0.7576(10) | 0.75644–0.75923 | ||||||||||||
36Cl [n 8] | 17 | 19 | 35.96830682(4) | 3.013(15)×105 y | β− (98.1%) | 36Ar | 2+ | Trace [n 9] | approx. 7×10−13 | ||||||||||
β+ (1.9%) | 36S | ||||||||||||||||||
37Cl | 17 | 20 | 36.96590258(6) | Stable | 3/2+ | 0.2424(10) | 0.24077–0.24356 | ||||||||||||
38Cl | 17 | 21 | 37.96801042(11) | 37.24(5) 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 | 39.97042(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 | 41.97334(6) | 6.8(3) s | β− | 42Ar | |||||||||||||
43Cl | 17 | 26 | 42.97406(7) | 3.13(9) s | β− (>99.9%) | 43Ar | (3/2+) | ||||||||||||
β−, n (<.1%) | 42Ar | ||||||||||||||||||
44Cl | 17 | 27 | 43.97812(15) | 0.56(11) s | β− (92%) | 44Ar | (2-) | ||||||||||||
β−, n (8%) | 43Ar | ||||||||||||||||||
45Cl | 17 | 28 | 44.98039(15) | 513(36) ms [7] | β− (76%) | 45Ar | (3/2+) | ||||||||||||
β−, n (24%) | 44Ar | ||||||||||||||||||
46Cl | 17 | 29 | 45.98512(22) | 232(2) ms | β−, n (60%) | 45Ar | 2-# | ||||||||||||
β− (40%) | 46Ar | ||||||||||||||||||
47Cl | 17 | 30 | 46.98950(43)# | 101(6) ms | β− (97%) | 47Ar | 3/2+# | ||||||||||||
β−, n (3%) | 46Ar | ||||||||||||||||||
48Cl | 17 | 31 | 47.99541(54)# | 100# ms [>200 ns] | β− | 48Ar | |||||||||||||
49Cl | 17 | 32 | 49.00101(64)# | 50# ms [>200 ns] | β− | 49Ar | 3/2+# | ||||||||||||
50Cl | 17 | 33 | 50.00831(64)# | 20# ms | β− | 50Ar | |||||||||||||
51Cl | 17 | 34 | 51.01534(75)# | 2# ms [>200 ns] | β− | 51Ar | 3/2+# | ||||||||||||
52Cl [8] | 17 | 35 | β− | 52Ar | |||||||||||||||
This table header & footer: |
IT: | Isomeric transition |
n: | Neutron emission |
p: | Proton emission |
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 36
Ar 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 40
Ca. 36Cl decays to either 36
S (1.9%) or to 36
Ar (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.
Stable chlorine-37 makes up about 24.23% of the naturally occurring chlorine on earth. Variation occurs as chloride mineral deposits have a slightly elevated chlorine-37 balance over the average found in sea water and halite deposits.[ citation needed]