<u>**Answer:**</u>** The percentage abundance of and isotopes are 37.10% and 62.90% respectively.**

<u>**Explanation:**</u>

**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:**

** .....(1)**

Let the fractional abundance of isotope be 'x'. So, fractional abundance of isotope will be '1 - x'

- <u>
**For isotope:**</u>

Mass of isotope = 190.9606 amu

Fractional abundance of isotope = x

- <u>
**For isotope:**</u>

Mass of isotope = 192.9629 amu

Fractional abundance of isotope = 1 - x

Average atomic mass of iridium = 192.22 amu

**Putting values in equation 1, we get:**

Percentage abundance of isotope =

Percentage abundance of isotope =

**Hence, the percentage abundance of and isotopes are 37.10% and 62.90% respectively.**