When comparing the atomic size contraction phenomena across the 4f and 5f series, it is observed tha — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Both contractions arise because $f$ -electrons shield the increasing nuclear charge poorly. However, $5f$ orbitals are much more diffuse/extended than $4f$ orbitals. Thus, $5f$ electrons offer exponentially worse shielding, pulling the outer shell inward more forcefully.