Remember the order \(s \textgreater p \textgreater d \textgreater f\). Poor shielding by d and f electrons is responsible for phenomena like Lanthanide contraction and the inert pair effect.
Step 1: Understanding the Concept:
Screening effect (or shielding effect) refers to the ability of inner-shell electrons to shield the outer-shell electrons from the full nuclear charge. This depends heavily on the shape and penetration power of the orbitals. Step 2: Detailed Explanation:
1. Orbitals that are more "spherical" and closer to the nucleus provide better shielding.
2. The order of penetration power is $s>p>d>f$. Because $s$ and $p$ orbitals are closer to the nucleus and have a more compact shape, they shield the nuclear charge very effectively.
3. $d$ and $f$ orbitals have diffused (spread out) shapes. This diffusion makes them poor shields.
4. Therefore, $d$-electrons provide less screening than $p$-electrons. Step 3: Final Answer
The screening effect of $d$-electrons is less than that of $p$-electrons.