Answer: 20.2
Explanation:
Mass of isotope 1 = 20
% abundance of isotope 1 = 90.5% = [tex]\frac{90.5}{100}=0.905[/tex]
Mass of isotope 2 = 22
% abundance of isotope 2 = 8.0% = [tex]\frac{8}{100}=0.08[/tex]
Mass of isotope 3 = 23
% abundance of isotope 3 = 1.5% = [tex]\frac{1.5}{100}=0.015[/tex]
Formula used for average atomic mass of an element :
[tex]\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})[/tex]
[tex]A=\sum[(20\times 0.905+(22\times 0.08)+(23\times 0.015][/tex]
[tex]A=20.2[/tex]
Therefore, the average atomic mass of the element is 20.2.
