A mystery element has three isotopes of the following masses and percent abundances: 93.597 amu at 23.63 % abundance, 96.191 amu at 30.53 % abundance, and 95.502 amu. What is the exact atomic mass of the mystery element?

92.397amu

Explanation: The exact amu of the mystery element is obtained by multiplying the relative abundance of each individual isotope by its respective amu and then summing the results.

The sum of the total relative abundance for all the isotopes should be 100%.

However, the relative abundance of the isotope with 95.502amu is not given; therefore to obtain it we subtract the sum of the known relative abundances from 100% as follows:

Relative abundance of isotope with 95.502amu = 100 - (23.63+30.53) = 42.84%