The variation in atomic sizes across transition elements is fundamentally governed by the shielding — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The shielding (or screening) effect depends upon the shape and electron density distribution of the orbital. Spherically symmetric $s$ -orbitals shield the nucleus most effectively. The $p$ -orbitals are directional and shield less effectively. The $d$ and $f$ orbitals have highly diffuse, complex shapes that allow significant nuclear charge to leak through, making them the poorest shielders. The order is $s > p > d > f$.