Question

The masses and relative abundances of all naturally occurring isotopes of the element are required to calculate average atomic mass of the element

Answer 1

Using the masses of the differentisotopes and how abundant each isotope is, we can find the average mass of the atoms of an element. The atomic mass of an element is the weighted average mass of the atoms in a naturally occurring sample of the element. Atomic mass is typically reported in atomic mass units.

Answer 2

In order to calculate the average atomic mass of element using masses and relative abundance==>

1. take the exact mass of each isotope (that will be in decimal form)

2. multiply the mass of each isotope by its abundance

3. add each of the results together.

This gives you the total atomic mass or weight of the element.

Example- Chlorine.

Change the percentages to their decimal forms:

24.47 % = 24.47 /100  =  0.2447

75.53 % = 75.53 /100 =  0.7553

Multiply the mass of each isotope by its percent abundance and add.  

0.2447(36.9590 u)+0.7553(34.96885 u)  = 35.46 u

:)