Which electronic configuration is not observing the ( n+ 1) rule:
(1) 1s2, 2s2, 2p6, 3s2, 3p6, 3d1, 4s2
(2) 1s2, sp2, sp6, 3s2, 3p6, 3d7, 4s2
(3) 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1
(4) 1s2, 2s2, 2p6, 3s2, 3p6, 3d8, 4s2
Ans: 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1