The atomic mass of an element is the weighted average of all of its isotopes. The percent abundance for the element boron is 19.9% boron-10 and 80.1% boron-11. Given the following atomic masses, determine the average atomic mass of the element boron.
Boron-10 has a mass of 10.0129370 amu
Boron-11 has a mass of 11.0093055 amu
.199 * 10.0129 + .801 * 11.009 = 1.0 * x
1.9926 + 8.818 = 10.81
To find the average atomic mass of boron, we can use the concept of weighted average.
First, we multiply the percent abundance of each isotope by its atomic mass:
For Boron-10:
(19.9% × 10.0129370 amu) = 1.9953102 amu
For Boron-11:
(80.1% × 11.0093055 amu) = 8.8086956 amu
Next, we add the two values together to get the weighted sum:
1.9953102 amu + 8.8086956 amu = 10.8030058 amu
Finally, we round the average atomic mass to the correct number of significant figures:
The average atomic mass of boron is approximately 10.8 amu.