Question

Consider the spectral line resulting from the transition n = 2 $\Rightarrow$ n = 1 in the atoms and ions given below. The shortest wavelength is produce by

• A. Hydrogen atom
• B. Deuterium atom
• C. Singly ionized helium
• D. Doubly ionized lithium

Answer 1

The correct option is D Doubly ionized lithium

$\frac{1}{\lambda }=R{Z}^2(\frac{1}{n_2^2}-\frac{1}{n_1^2})\therefore \frac{1}{\lambda }\propto Z^2$
$\lambda$ is shortest if Z is largest. Z is largest for doubly ionized lithium atom (Z = 3) among the given elements.
Hence wavelength for double ionized lithium will be the least.