If bromine atom is available in the form of, say, two isotopes 79 35Br (49.7%) and 81 35Br (50.3%), calculate the average atomic mass of bromine atom.
Answer
We know the percentage of is 49.7%
And the percentage of is 50.3%
We know that,
Average mass of an isotope = (% existence of the isotope 1 x mass of isotope 1) +
(% existence of the isotope 2 x mass of isotope 2)
= (M1 x P1) + (M2 x P2)
= (79 x 49.7 /100) + (81 x 50.3/100)
= (79 x 497/1000) + (81 x 503 /1000)
= (39263/ 1000) + (40743/1000)
= 39.263 + 40.743
= 80.006u
Thus, the average atomic mass of bromine is 80u.
