The hydrogen -like species `Li^(2+)` is in a spherically symmetric state `S_(1)` with one node. Upon absorbing light , the ion undergoes transition to a state `S_(2)`. The state `S_(2)` has one radial node and its energy is equal is to the ground state energy of the hydrogen atom.
The sate `S_(1)` is

Options

A. 1 s
B. 2 s
C. `2 p`
D. 3 s

Answer

B

Explanation

The state `S_(1)` in case of `Li^(2+)`ion must be 2s (It has one radial mode). It must have jumped to 3p (`S_(2)` state) which has one radial node and its energy is equal to that of ground state of H atom
`E_(H)(1 s)=-13.6 eV`
`E_(Li^(2+))(3p)=(-13.6 Z^(2))/(n^(2))=-(13.6xx(3)^(2))/((3)^(2))`
`=-13.6 eV`