An element $Y$ has the following observed isotopic composition: $^{20}\mathrm{Y}$ (80%), $^{21}\math

Question

An element $Y$ has the following observed isotopic composition: $^{20}\mathrm{Y}$ (80%), $^{21}\mathrm{Y}$ (10%), and $^{22}\mathrm{Y}$ (10%). The weighted average atomic mass of the naturally occurring element $Y$ is closest to

Professor PC Thomas Classes · Answer

(b) : The average isotopic mass of element $Y$ is calculated as $\frac{\sum (	ext{Isotope Mass} 	imes 	ext{Abundance})}{100}$. Substituting the values: $\frac{(20 	imes 80) + (21 	imes 10) + (22 	imes 10)}{100} = \frac{1600 + 210 + 220}{100} = \frac{2030}{100} = 20.3 \mathrm{~amu}$.