Answer: The average atomic mass of lithium is 6.9241 u.
Explanation:
Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.
Formula used to calculate average atomic mass follows:
[tex]\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i[/tex] ....(1)
Mass of [tex]_3^6\textrm{Li}[/tex] isotope = 6 u
Percentage abundance of [tex]_3^6\textrm{Li}[/tex] isotope = 7.59 %
Fractional abundance of [tex]_3^6\textrm{Li}[/tex] isotope = 0.0759
Mass of [tex]_3^7\textrm{Li}[/tex] isotope = 7 u
Percentage abundance of [tex]_3^7\textrm{Li}[/tex] isotope = 92.41%
Fractional abundance of [tex]_3^7\textrm{Li}[/tex] isotope = 0.9241
Putting values in equation 1, we get:
[tex]\text{Average atomic mass of Lithium}=[(6\times 0.0759)+(7\times 0.9241)][/tex]
[tex]\text{Average atomic mass of Lithium}=6.9241u[/tex]
Hence, the average atomic mass of lithium is 6.9241 u.
