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

Answer

B

Explanation

for lower state `(S_1)`
No. of radial node = 1=n-l-1
Put n=2 and l=0 (as higher state `S_2` has n=3)
So, it would be 2s (for `S_1` state)