Boron Has Primarily Two Isotopes, One with an Atomic Mass

Multiple Choice

Boron has primarily two isotopes, one with an atomic mass of 11.0 amu and another with an atomic mass of 10.0 amu. If the abundance of the boron atom with a mass of 11.0 amu is 18.9 percent and the abundance of the other isotope is 81.1 percent, what would be the average mass of the boron atom?

A) 10.2 amu
B) 11.0 amu
C) 10.0 amu
D) 10.8 amu
E) not enough information given