Answer
To calculate the average atomic mass of an element, the exact atomic mass of each of the isotopes of that element, and the isotopic abundances would have to be given. You would then take the weighted average of the different isotopes based on the abundance percentages.
Work Step by Step
Average atomic masses are an average of all the atomic masses of the isotopes of an element, so a weighted average of the atomic masses of the different isotopes must be taken with respect to their abundances in nature.
