Chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...

(₁₇Cl) has 25 isotopes with mass numbers ranging from ²⁸Cl to ⁵²Cl and 2

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. ...

(^34mCl and ^38mCl). There are two stable isotopes, ³⁵Cl (75.77%) and ³⁷Cl (24.23%), giving chlorine a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, ...

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 10 picoseconds and 30 nanoseconds, respectively—the half-life of ²⁸Cl is unknown.

List of isotopes

, - , ²⁸Cl , style="text-align:right" , 17 , style="text-align:right" , 11 , 28.02954(64)# , , p , ²⁷S , 1+# , , , - , ²⁹Cl , style="text-align:right" , 17 , style="text-align:right" , 12 , 29.01413(20) , <10 ps , p , ²⁸S , (1/2+) , , , - , ³⁰Cl , style="text-align:right" , 17 , style="text-align:right" , 13 , 30.00477(21)# , <30 ns , p , ²⁹S , 3+# , , , - , rowspan=2, ³¹Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 14 , rowspan=2, 30.992448(4) , rowspan=2, 190(1) ms , β⁺ (97.6%) , ³¹S , rowspan=2, 3/2+ , rowspan=2, , rowspan=2, , - , β⁺, p (2.4%) , ³⁰P , - , rowspan=3, ³²Cl , rowspan=3 style="text-align:right" , 17 , rowspan=3 style="text-align:right" , 15 , rowspan=3, 31.9856846(6) , rowspan=3, 298(1) ms , β⁺ (99.92%) , ³²S , rowspan=3, 1+ , rowspan=3, , rowspan=3, , - , β⁺, α (.054%) , ²⁸Si , - , β⁺, p (.026%) , ³¹P , - , ³³Cl , style="text-align:right" , 17 , style="text-align:right" , 16 , 32.9774520(4) , 2.5038(22) s , β⁺ , ³³S , 3/2+ , , , - , ³⁴Cl , style="text-align:right" , 17 , style="text-align:right" , 17 , 33.97376249(5) , 1.5266(4) s , β⁺ , ³⁴S , 0+ , , , - , rowspan=2 style="text-indent:1em" , ^34mCl , rowspan=2 colspan="3" style="text-indent:2em" , 146.360(27) keV , rowspan=2, 31.99(3) min , β⁺ (55.4%) , ³⁴S , rowspan=2, 3+ , rowspan=2, , rowspan=2, , - , IT (44.6%) , ³⁴Cl , - , ³⁵Cl , style="text-align:right" , 17 , style="text-align:right" , 18 , 34.96885269(4) , colspan=3 align=center, Stable , 3/2+ , 0.7576(10) , 0.75644–0.75923 , - , rowspan=2, ³⁶ClUsed in

radiodating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...

water , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 19 , rowspan=2, 35.96830682(4) , rowspan=2, 3.013(15)×10⁵ y , β⁻ (98.1%) , ³⁶Ar , rowspan=2, 2+ , rowspan=2, Trace

Cosmogenic nuclide Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an ''in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ...

, rowspan=2, approx. 7×10⁻¹³ , - , β⁺ (1.9%) , ³⁶S , - , ³⁷Cl , style="text-align:right" , 17 , style="text-align:right" , 20 , 36.96590258(6) , colspan=3 align=center, Stable , 3/2+ , 0.2424(10) , 0.24077–0.24356 , - , ³⁸Cl , style="text-align:right" , 17 , style="text-align:right" , 21 , 37.96801042(11) , 37.24(5) min , β⁻ , ³⁸Ar , 2− , , , - , style="text-indent:1em" , ^38mCl , colspan="3" style="text-indent:2em" , 671.365(8) keV , 715(3) ms , IT , ³⁸Cl , 5− , , , - , ³⁹Cl , style="text-align:right" , 17 , style="text-align:right" , 22 , 38.9680082(19) , 56.2(6) min , β⁻ , ³⁹Ar , 3/2+ , , , - , ⁴⁰Cl , style="text-align:right" , 17 , style="text-align:right" , 23 , 39.97042(3) , 1.35(2) min , β⁻ , ⁴⁰Ar , 2− , , , - , ⁴¹Cl , style="text-align:right" , 17 , style="text-align:right" , 24 , 40.97068(7) , 38.4(8) s , β⁻ , ⁴¹Ar , (1/2+,3/2+) , , , - , ⁴²Cl , style="text-align:right" , 17 , style="text-align:right" , 25 , 41.97334(6) , 6.8(3) s , β⁻ , ⁴²Ar , , , , - , rowspan=2, ⁴³Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 26 , rowspan=2, 42.97406(7) , rowspan=2, 3.13(9) s , β⁻ (>99.9%) , ⁴³Ar , rowspan=2, (3/2+) , rowspan=2, , rowspan=2, , - , β⁻, n (<.1%) , ⁴²Ar , - , rowspan=2, ⁴⁴Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 27 , rowspan=2, 43.97812(15) , rowspan=2, 0.56(11) s , β⁻ (92%) , ⁴⁴Ar , rowspan=2, (2-) , rowspan=2, , rowspan=2, , - , β⁻, n (8%) , ⁴³Ar , - , rowspan=2, ⁴⁵Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 28 , rowspan=2, 44.98039(15) , rowspan=2, 413(25) ms , β⁻ (76%) , ⁴⁵Ar , rowspan=2, (3/2+) , rowspan=2, , rowspan=2, , - , β⁻, n (24%) , ⁴⁴Ar , - , rowspan=2, ⁴⁶Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 29 , rowspan=2, 45.98512(22) , rowspan=2, 232(2) ms , β⁻, n (60%) , ⁴⁵Ar , rowspan=2, 2-# , rowspan=2, , rowspan=2, , - , β⁻ (40%) , ⁴⁶Ar , - , rowspan=2, ⁴⁷Cl , rowspan=2 style="text-align:right" , 17 , rowspan=2 style="text-align:right" , 30 , rowspan=2, 46.98950(43)# , rowspan=2, 101(6) ms , β⁻ (97%) , ⁴⁷Ar , rowspan=2, 3/2+# , rowspan=2, , rowspan=2, , - , β⁻, n (3%) , ⁴⁶Ar , - , ⁴⁸Cl , style="text-align:right" , 17 , style="text-align:right" , 31 , 47.99541(54)# , 100# ms 200 ns, β⁻ , ⁴⁸Ar , , , , - , ⁴⁹Cl , style="text-align:right" , 17 , style="text-align:right" , 32 , 49.00101(64)# , 50# ms 200 ns, β⁻ , ⁴⁹Ar , 3/2+# , , , - , ⁵⁰Cl , style="text-align:right" , 17 , style="text-align:right" , 33 , 50.00831(64)# , 20# ms , β⁻ , ⁵⁰Ar , , , , - , ⁵¹Cl , style="text-align:right" , 17 , style="text-align:right" , 34 , 51.01534(75)# , 2# ms 200 ns, β⁻ , ⁵¹Ar , 3/2+# , , , - , ⁵²Cl , style="text-align:right" , 17 , style="text-align:right" , 35 , , , β⁻ , ⁵²Ar , , ,

Chlorine-36

Trace amounts of

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...

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 Muon capture is the capture of a negative muon by a proton, usually resulting in production of a neutron and a neutrino, and sometimes a gamma photon. Muon capture by heavy nuclei often leads to emission of particles; most often neutrons, but ...

by ⁴⁰ Ca. ³⁶Cl decays to either ³⁶ S (1.9%) or to ³⁶ Ar (98.1%), with a combined

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 308,000 years. The half-life of this

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are no ...

nonreactive isotope makes it suitable for

geologic dating Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is ...

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 Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...

, 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 by neutron capture is an inevitable consequence of using natural isotope mixtures of chlorine (i.e. Those containing ). This produces a long lived radioactive product which has to be stored or disposed off.

Isotope separation Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. The use of the nuclides produced is varied. The largest variety is used in research (e.g. in chemistry where atoms of "marker" ...

to produce pure can vastly reduce production, but a small amount might still be produced by (n,2n) reactions involving

fast neutron The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium with ...

Chlorine-37

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.

References

External links

Chlorine isotopes data from ''The Berkeley Laboratory Isotopes Project's''
{{Navbox element isotopes Chlorine