Question

i want answer for this question

Answer 1

We know that upper digit in the symbol of an isotope represents its mass (which is the same as its mass number). Now:
(i) The mass of  isotope is 79 u and its abundance is 49.7%.
(ii) The mass of  isotope is 81 u and its abundance is 50.3%.
So, Average atomic mass of bromine = (79×49.7)+(81×50.3)/100
= 3926.3 + 4074.3/100
= 8000.6/100 = 80 u
Thus, the average atomic mass of bromine is 80 u.

Answer 2

average atomic mass of bromine is 78.92 amu