Question

Bromine atom is available in two isotopes, ${}_{35}^{79}Br$ (49.7%) and ${}_{35}^{81}Br$ $\left(50.3\%\right)$, the average atomic mass of bromine atom is :

• A. $79.016$
• B. $80.076$
• C. $80.006$
• D. $81.016$

Answer 1

The correct option is

C

$80.006$

The average atomic mass is the average mass of the atoms in the naturally occurring sample of the element. The average atomic mass of an element is the sum of the mass of its isotopes each multiplied by its natural abundance.

It is given that two isotopes of Bromine are 79/35 Br(49.7%) and 81/35 Br(50.3%). Then, the average atomic mass of the Bromine atom is given by

Avg Atomic Weight = $79\times \frac{49.7}{100}+81\times \frac{50.3}{100}$ = 80.006

Option C is correct