Question

If a bromine atom is available in the form of, say two isotopes, $$(^{79}_{35}\mathrm{Br}) (49.7\%)$$ and $$(^{81}_{35}\mathrm{Br}) (50.3\%)$$, calculate the average atomic mass of the bromine atom.

Answer 1

Weighted average atomic mass = (79 × 0.497) + (81 × 0.503) = 80.006 u, or approximately 80.01 u.