Answer :
Answer: 28.1 amu
Explanation:
Mass of isotope 1 = 27.98 amu
% abundance of isotope 1 = 92.21% = [tex]\frac{92.21}{100}=0.9221[/tex]
Mass of isotope 2 = 28.98 amu
% abundance of isotope 2 = 4.70% = [tex]\frac{4.70}{100}=0.047[/tex]
Mass of isotope 3 = 29.97 amu
% abundance of isotope 2 = 3.09% = [tex]\frac{3.09}{100}=0.0309[/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[(27.98 )\times 0.922+(28.98)\times 0.047+(29.97)\times 0.0309][/tex]
[tex]A=28.1amu[/tex]
Therefore, the average atomic mass of silicon is 28.1 amu