Question

For the imaginary element abdicinium (Ab), two isotopes exist. Isotope one has a mass of 40.005 amu with a relative abundance of 14.00%. Isotope two has a mass of 41.008 amu with a relative abundance of 86.00%. What is the atomic mass of the element

Answer 1

Answer: The average atomic mass of abdicinium is 40.8676 amu

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$   .....(1)

• For isotope 1:

Mass of isotope 1 = 40.005 amu

Percentage abundance of isotope 1 = 14.00 %

Fractional abundance of isotope 1 = 0.1400

• For isotope 2:

Mass of isotope 2 = 41.008 amu

Percentage abundance of isotope 2 = 86.00 %

Fractional abundance of isotope 2 = 0.8600

Putting values in equation 1, we get:

$\text{Average atomic mass of abdicinium}=[(40.005\times 0.1400)+(41.008\times 0.8600)]\\\\\text{Average atomic mass of abdicinium}=40.8676amu$

Hence, the average atomic mass of abdicinium is 40.8676 amu