Further data for radioisotopes (radioactive isotopes) of chlorine are listed separately (including any which occur naturally) in the radioisotopes section. This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances, their nuclear spins, and their magnetic moments.

Isotope	Atomic mass (ma/u)	Natural abundance (atom %)	Nuclear spin (I)	Magnetic moment (μ/μN)
35Cl	34.968852721 (69)	75.78 (4)	3/2	0.8218736
37Cl	36.96590262 (11)	24.22 (4)	3/2	0.6841230

In the above picture, the most intense ion is set to 100% since this corresponds best to the output from a mass spectrometer. This is not to be confused with the relative percentage isotope abundances which total 100% for all the naturally occurring isotopes.