What is the wave number of the radiation of lowest frequency in the Lyman series of the spectrum of — Atomic Structure Chemistry Question

💡 Solution & Explanation

Lowest frequency in the Lyman series means the lowest energy transition, which is from $n_2=2$ to $n_1=1$. For $Li^{2+}$, $Z=3$. Wave number $\bar{\nu} = \frac{1}{\lambda} = R Z^2 \left(\frac{1}{1^2} - \frac{1}{2^2}\right) = R(3)^2 \left(1 - \frac{1}{4}\right) = 9R \left(\frac{3}{4}\right) = \frac{27 R}{4}$. Therefore, correct answer is B.