Column Descriptions Relative Isotopic Standard Isotope Atomic Mass Composition Atomic Weight Notes _________________________________________________________________________ 82 Pb 204 203.9730440(13) 0.014(1) 207.2(1) g,r 206 205.9744657(13) 0.241(1) 207 206.9758973(13) 0.221(1) 208 207.9766525(13) 0.524(1) _________________________________________________________________________NIST | Physical Measurement Laboratory | Physical Reference Data | Atomic Weights and Isotopic Compositions Main Page