Question

A newly discovered element consists of 2 isotopes, one with a mass of 9.5 and a relative abundance of 17.2% and another with a mass of 2.2 and a relative abundance of 82.8%. Determine the atomic weight of the new element.

Answer 1

0.172*9.5 + 0.828*2.2 = 3.4566

Answer 2

Note that atomic weights are weighted averages of the isotopes.