Question

What is shortest wavelength line in the Paschen series of ${Li}^{2+}$ ion?

Answer 1

We know that,

$\frac{1}{\lambda }=R{Z}^2(\frac{1}{n_1^2}-\frac{1}{n_2^2})$

For Paschen series, $n_1=3$ and $n_2=\infty$ (For shortest wavelength)

$Z=2$

On substituting above values in the equation,

$⟹\lambda =\frac{9}{4R}$