Atomic Weights and Isotopic Compositions for Protactinium
Column Descriptions

                                                                         
             Relative           Isotopic      Standard                   
Isotope      Atomic Mass        Composition   Atomic Weight    Notes     
_________________________________________________________________________
91  Pa  231  231.0358842(24)    1             231.03588(2)      
_________________________________________________________________________

NIST | Physical Measurement Laboratory | Physical Reference Data | Atomic Weights and Isotopic Compositions Main Page