Boron obtained from borax deposits in Death Valley consists of two isotopes. They are boron-10 and boron-11 with atomic masses of 10.013 amu and 11.009 amu, respectively. The atomic mass of boron is 10.81 amu (see periodic table). Which isotope of boron is more abundant, boron-10 or boron-11
A) Cannot be determined from data given
B) Neither, their abundances are the same.
C) Boron-10
D) Boron-11

Question

Quizplus · Accepted Answer

The atomic mass of boron is closer to that of boron-11 (11.009 amu) than to boron-10 (10.013 amu), indicating that boron-11 is more abundant. This is because the average atomic mass reflects the weighted average of the isotopes, weighted by their abundances.

Boron Obtained from Borax Deposits in Death Valley Consists of Two