Chapter 9, Problem 43TS

Chlorine (atomic number 17) is composed of two principle isotopes, chlorine-35, which has mass of $34.9689$ atomic units and chlorine-37, which has a mass of $36.9659$ atomic mass units. Assume that $75.77\%$ of all chlorine atoms are chlorine-35 isotopes and $24.23\%$ are the chlorine-37 isotope. Show that the atomic mass of natural chlorine is $35.45\text{amu}$.