Answer: B. Relative abundance of each isotope
Explanation:
Average atomic mass is the average mass of all the isotopes present depending on the relative abundance of each isotope.
\(\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i\)
Example:
Mass of isotope 1 = 203.973 amu
relative abundance of isotope 1 = 0.014
Mass of isotope 2 = 205.9745 amu
relative abundance of isotope 2= 0.241
Mass of isotope 3 = 206.9745 amu
relative abundance of isotope 3 = 0.221
Mass of isotope 4 = 207.9766 amu
relative abundance of isotope 4 = 0.574
Formula used for average atomic mass of an element :
\(\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})\)
\(\text{ Average atomic mass of an element}=\sum[(203.973\times0.014)+(205.9745\times 0.241)+(206.9745\times 0.221)+(207.9766\times 0.574)]\)
\(\text{ Average atomic mass of an element}=209.613amu\)
