An electron initially in a 4p state decays to a lower energy state.Which energy state is forbidden?
A) 3d
B) 2p
C) 2s
D) 1s

Question

Quizplus · Accepted Answer

The selection rules for electronic transitions in atoms dictate that for a transition to be allowed, the change in the orbital angular momentum quantum number ($l$) must be $\pm 1$. The 4p to 2p transition violates this rule because both initial and final states have the same $l$ value ($l = 1$ for p orbitals), making this transition forbidden.

An Electron Initially in a 4p State Decays to a Lower