Consider the elements belonging to the transition series (d-block). Which of the following statement — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Statement A represents lanthanide contraction (poor shielding by $4f$). Statement B outlines the standard d-block radius trend. Statement C is true because the extremely poor shielding of $4f$ electrons in $5d$ elements sharply increases $Z_{eff}$, making electrons harder to remove. Statement D is incorrect; transition metals typically have negative or mildly exothermic electron gain enthalpies, not highly endothermic.