The atomic masses of 79Br35 (50.69 percent) and 81Br35 (49.31 percent) are 78.9183361 and 80.916289 amu, respectively. Calculate the average atomic mass of bromine. The percentages in parentheses denote the relative abundances.

79.90amu

Explanation:

To calculate the average atomic mass of an bromine we must multiply the masses of its isotopes with the percent abundance divided by 100. Then you add them together for your answer.

50.69 : 100 = 0.5069

49.31 : 100 = 0.4931

78.9183361amu * 0.5069 = 40.00amu

80.916289amu * 0.4931 = 39.90amu

40.00amu + 39.90amu = 79.90amu