Answer : The boron-11 isotope is the most abundant.
Explanation :
As we are given that:
Average atomic mass of boron = 10.81 amu
Mass of boron-10 = 10.0129 amu
Mass of boron-11 = 11.0093 amu
As we know that the average atomic mass of an element is always closest to the most abundant isotope.
Out of the two boron isotopes, B-11 is closest in mass to the weighted average. Therefore, it is the most abundant.
Hence, the boron-11 isotope is the most abundant.
