Column Descriptions Relative Isotopic Standard Isotope Atomic Mass Composition Atomic Weight Notes _________________________________________________________________________ 17 Cl 35 34.968852682(37) 0.7576(10) [35.446,35.457] m 37 36.965902602(55) 0.2424(10) _________________________________________________________________________NIST | Physical Measurement Laboratory | Physical Reference Data | Atomic Weights and Isotopic Compositions Main Page