Question

The mass number of three isotopes of an element are 10, 12, 14 units. their percentage abundance is 80, 15 and 5 respectively. what is the atomic weight of the element?

Answer 1

it is the formula multiple each weight with their percentage and add all of them. the final answer is the avg.

Answer 2

Answer: The atomic weight of the element is 10.5 units.

Explanation:

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

Formula that is used to calculate the average atomic mass follows:

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

We are given:

Mass of isotope 1 = 10 u

Percentage abundance of isotope 1 = 80 %

Fractional abundance of isotope 1 = 0.80

Mass of isotope 2 = 12 u

Percentage abundance of isotope 2 = 15 %

Fractional abundance of isotope 2 = 0.15

Mass of isotope 3 = 14 u

Percentage abundance of isotope 3 = 5 %

Fractional abundance of isotope 3 = 0.05

Putting values in above equation, we get:

$\text{Average atomic mass of element}=[(10\times 0.80)+(12\times 0.15)+(14\times 0.05)]$

$\text{Average atomic mass of element}=10.5u$

Hence, the atomic weight of the element is 10.5 units.