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If bromine atom is available in the form of, say, two isotopes, _{35}\textrm{Br}^{79} (49.7%) and _{35}\textrm{Br}^{81} (50.3%), calculate the average atomic mass of bromine.
 
The formula to find average atomic mass is
 
a. Massofisotopes×%Naturalabundance100
b. Massofisotopes×100%Naturalabundance
c. %Naturealabundance×100Massofisotopes
When substituting the given values in the formula, we get,