<Tr> <Td_colspan="2"> <Ul> <Li> view </Li> <Li> talk </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> view </Li> <Li> talk </Li> <Li> </Li> </Ul> <P> Chlorine (Cl) has 24 isotopes with mass numbers ranging from Cl to Cl and 2 isomers (Cl and Cl). There are two principal stable isotopes, Cl (75.78%) and Cl (24.22%), giving chlorine a standard atomic weight of 35.45 . The longest - lived radioactive isotope is Cl, 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 Cl and Cl, with half - lives less than 20 and 30 nanoseconds, respectively--the half - life of Cl is unknown . </P> <P> Trace amounts of radioactive Cl exist in the environment, in a ratio of about 7 × 10 to 1 with stable isotopes . Cl is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons . In the subsurface environment, Cl is generated primarily as a result of neutron capture by Cl or muon capture by Ca . Cl decays to either S (1.9%) or to 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 Cl were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958 . The residence time of Cl in the atmosphere is about 1 week . Thus, as an event marker of 1950s water in soil and ground water, Cl is also useful for dating waters less than 50 years before the present . Cl has seen use in other areas of the geological sciences, forecasts, and elements . </P>

What does the 35 in the name chlorine-35 represent
find me the text answering this question