The atomic masses of 79 br 35 (50.69 percent) and 81 br 35 (49.31 percent) are 78.9183361 amu and 80.916289 amu, respectively. calculate the average atomic mass of bromine. the percentages in parentheses denote the relative abundances.

These 2 isotopes are all of bromine that is naturally found (their percentages add up to 100%). In order to calculate the mean atomic mass, we can use the following calculation: . This yields an average atomic mass of 79.903 amu. This procedure is general; whenever we have many types F of a specific genre G, the mean of the genre G can be calculated by:

where is the proportion of type i in the genre G. In this example, Br79 and Br81 are the 2 types and the genre is Bromine.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.