Chlorine Chlorine is a chemical element with the Symbol (chemistry), 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 betwee ...

(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. Iso ...

(^34mCl and ^38mCl). There are two stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

s, 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, is ...

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 Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...

of ³⁶ Ar by interactions with

cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s. In the subsurface environment, ³⁶Cl is generated primarily as a result of

neutron capture Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, ...

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 c ...

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 pr ...

in the range of 60,000 to 1 million years. Additionally, large amounts of ³⁶Cl were produced by neutron irradiation of

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

during atmospheric detonations of

nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...

s 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 Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

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 unconsolidated ...

, 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 reactor A molten salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a molten salt mixture. Only two MSRs have ever operated, both research reactors in the United States. The 1950's Ai ...

s the production of by

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" n ...

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 Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

deposits.

References

External links

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