Question

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

Answer 1

It is given that two isotopes of bromine are $^{79}Br_{35}$ (49.7%) and $^{81} Br_{35}$ (50.3%).

Then, the average atomic mass of bromine atom is = 7$9 \times \frac{49.7}{100} + 81 \times \frac{ 50.3}{100}$

= $\frac{2926.3}{100} + \frac{4074.3}{100}$

= $\frac{8000.6}{100}$
= $80.006$ u