Question

Hydrogen (¹₁H) ; deuterium (²₁H) , singly ionised helium (⁴₂H) and doubly ionised lithium (⁸₂Li)⁺⁺, all have only one electron orbiting around the nucleus. Consider an electron transition from n = 2 to n = 1. If the wavelengths emitted are λ₁, λ₂, λ₃ and λ₄, respectively, for these four atoms/ions. Then (approximately) which one of the followings is correct? 

Answer 1

Correct option : (3)

Explanation :

For a hydrogen like atom, of atomic number z; for the given transition, we have

Here R is Rydberg’s constant, for hydrogen. For the given four atoms z₁ = 1, z₂ = 1, z₃ = 2, and z₄ = 3. Therefore