If I understand right, the rules are: Suppose we want to find net effective charge on an electron in the nth shell. 1) We should ignore the electrons in the higher shells. 2) Every electron in the same shell shield by 0.35 except 1s orbital where electrons shield by 0.3 3)Every electron in (n-1)th shell shield by 0.85 for s and p orbitals; and 1 for d, f orbitals. 3)All other electrons shield by 1. Now, I want to know that if there are any exceptions for this especially with the second point above. I heard it is something like, for d orbitals, all electrons in same shell shield by 1. Is that true? Or are the above rules are final?