Boron naturally occurs in two isotopic forms. The more common isotope is ¹¹B (atomic mass 11.01 amu), which is 80.00% abundant. The average atomic mass of boron is 10.81. What is the mass of the other isotope?

Question

Quizplus · Accepted Answer

To find the mass of the other isotope, use the formula for average atomic mass: (mass of isotope 1)(% abundance of isotope 1) + (mass of isotope 2)(% abundance of isotope 2) = average atomic mass. Given that the more common isotope has a mass of 11.01 amu and an abundance of 80%, and the average atomic mass of boron is 10.81 amu, we can set up the equation: (11.01)(0.80) + (mass of isotope 2)(0.20) = 10.81. Solving for the mass of isotope 2 gives a value of approximately 10.01 amu.

Boron Naturally Occurs in Two Isotopic Forms