The atomic weight of a newly discovered element is 98.225 amu. it has two naturally occuring isotopes. one isotope has a mass of 96.780 amu. the second isotope has a percent abundance of 41.7%. what is the mass of the second isotope?

Atomic weight of an element can be calculated as follows:

average atomic weight =

(atomic weight of first isotope) (its percentage of abundance) +

(atomic weight of second isotope) (its percentage of abundance)

average atomic weight = 98.225 amu

atomic weight of first isotope = 97.780 amu

its percentage of abundance = 1 - 0.417 = 0.583

atomic weight of second isotope = ?

its percentage of abundance = 0.417

So, just substitute in the above equation to get the atomic weight of the second isotope as follows:

98.225 = (97.78) (0.583) + (mass2) (0.417)

atomic weight of second isotope = 98.847 amu