Rhenium (Re) is made up of 37.4% 185Re and 62.6% 187Re. The atomic mass of 185Re is 184.953 amu. The atomic mass of 187Re is 186.958 amu. What is the average atomic mass of rhenium?

To calculate the average mass of the element, we take the summation of the product of the isotope and the percent abundance. We calculate as follows:

Average atomic mass =.374 (184.953 amu) +.626 (186.958 amu) = 186.208 amu

Hope this answers the question. Have a nice day.