The order of screening effect of electrons of s, p, d and f orbitals of a given shell of an atom on electrons in its outer shell is :

1. s > p > d > f

2. f > d > p > s

3. p < d < f < s

4. f > p > s > d

How does the shielding effect of d-electrons compare to that of other electrons?

1. Weaker than s-electrons.
2. Stronger than s-electrons.  
3. Same as s-electrons.
4. Same as p-electrons.