Bromine has two isotopes having the relative abundance as 75Br39 = 50.51% and 81Br35 = 49.49%.the average atomic mass of bromine is

Explanation

To calculate the average atomic mass of bromine, we consider the weighted average of the individual isotope masses and their relative abundances:Define isotope masses and abundances:⁷⁹Br³⁵: mass = 78.99 amu, abundance = 50.51%¹⁸¹Br³⁵: mass = 80.916 amu, abundance = 49.49%Calculate the weighted average:Average atomic mass = (mass of ⁷⁹Br³⁵ * abundance of ⁷⁹Br³⁵) + (mass of ¹⁸¹Br³⁵ * abundance of ¹⁸¹Br³⁵)Average atomic mass = (78.99 amu * 0.5051) + (80.916 amu * 0.4949)Average atomic mass ≈ 79.915 amu (rounded to three decimal places)Therefore, the average atomic mass of bromine is approximately 79.915 amu, which is closest to option b.80.