Question

A generic element, G, is composed of two isotopes, 132G and 128G. 132G has a natural abundance of 90% and an isotopic mass of 131.90 amu, and 128G has a natural abundance of 10% and an isotopic mass of 127.90 amu. What is the average atomic mass of this element?

Answer 1

Answer: The average atomic mass of this element is 131.5 amu

Explanation:

Mass of isotope 1 = 131.90 amu

% abundance of isotope 1 = 90% = $\frac{90}{100}=0.9$

Mass of isotope 2 = 127.90 amu

% abundance of isotope 2 = 10% = $\frac{10}{100}=0.1$

Formula used for average atomic mass of an element :

$\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})$

$A=\sum[(131.90\times 0.9)+(127.90\times 0.1)]=131.5amu$

The average atomic mass of this element is 131.5 amu