1. The problem statement, all variables and given/known data Determine if the electron transitions are "allowed" or "forbidden" using the transition rules: i. 2p→2s ii. 1s→2p iii. 3d→2p iv. 3d→1s v. 4s→2p 2. Relevant equations Δl = ±1, Δml= 0, ±1 E = (-2.18*10-18eV)(1/n12 - 1/n22) 3. 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?