If bromine atom is available in the form of, say, two isotopes (49.7%) and (50.3%), calculate the average atomic mass of bromine atom. Solution : Isotope of bromine with atomic mass 79 u = 49.7%Therefore, Contribution of (_35^79)Br to atomic mass = (79*49.7)/100 = 39.26 u
Isotope of bromine with atomic mass 81 u = 50.3%
Contribution of (_35^81)Br to the atomic mass of bromine = (81*50.3)/100 = 40.64u
Hence atomic mass of the bromine atom = 39.26 + 40.64 u = 80u
