Column Descriptions Relative Isotopic Standard Isotope Atomic Mass Composition Atomic Weight Notes _________________________________________________________________________ 75 Re 185 184.9529545(13) 0.3740(2) 186.207(1) 187 186.9557501(16) 0.6260(2) _________________________________________________________________________NIST | Physical Measurement Laboratory | Physical Reference Data | Atomic Weights and Isotopic Compositions Main Page