Historical Atomic Weights
Summarized below are all standard atomic-weight values recommended by the CIAAW since its inaugural 1902 Atomic Weight Table.
Please enter the name or symbol of the element, or the year in order to retrieve the relevant historical standard atomic weights.
An entry is given only when the Commission recommended for the element a revised (or new) atomic-weight value. All values are given here as originally published by the Commission. Note that in 1961, the basis for expressing the atomic-weight values has been changed from ma(O) = 16 to ma(12C) = 12.
All names and symbols of the elements are given in their present form even though many changes have occured in this regard over the last century.
© CIAAW 2016 (updated in Aug 2016)