Because of the lanthanide contraction, which of the following pairs of elements have nearly the iden — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Lanthanide contraction is the steady decrease in size of the atoms and ions of rare earth elements (from La to Lu) due to the poor shielding of the 14 $4f$ electrons. This contraction exactly cancels out the expected size increase from the 4d to 5d transition series in the same group. Therefore, $Zr$ (4d) and $Hf$ (5d), both in Group 4, possess nearly identical radii.