Determine if the electron transitions are "allowed" or "forbidden" using the transition rules:
Δl = ±1, Δml= 0, ±1
E = (-2.18*10-18eV)(1/n12 - 1/n22)
The Attempt at a Solution
I know iv. is forbidden because Δl is greater than 1, but what about the others? If i. is allowed then the energy is 0eV, which I think is not possible because photos are emitted. May anyone please offer a brief explanation to why it is allowed?