Chlorine naturally exists in two distinct isotopic forms, $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$,

Question

Chlorine naturally exists in two distinct isotopic forms, $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$, with relative percentage abundances of 75% and 25% respectively. The weighted average atomic mass of chlorine is

Professor PC Thomas Classes · Answer

(a) : The average atomic mass is the weighted sum of the isotopic masses. Average atomic mass = $\frac{(35 	imes 75) + (37 	imes 25)}{100} = \frac{2625 + 925}{100} = \frac{3550}{100} = 35.5 \mathrm{~u}$.