To calculate the atomic mass of bromine, we need to consider the weighted average of the masses of its isotopes, taking into account their relative abundances.
Let's denote the atomic mass of bromine as X.
Given that 50% of bromine has a mass of 79 (let's denote this isotope as Br-79) and 49% has a mass of 81 (let's denote this isotope as Br-81), we can set up the following equation:
(0.50 * X) + (0.49 * X) = 79 + 81
0.99 * X = 160
Dividing both sides of the equation by 0.99:
X ≈ 161.62
Therefore, the atomic mass of bromine is approximately 161.62 atomic mass units (amu).