The second and third members in each group of the transition elements have similar metallic radii. Assing reason.

Explanation

This is because of lanthanoid contraction in the members of the lanthanoid family (Z=58 to Z=71) which occupy a position along with Lanthaum (Z=57) in the perodicd table. However, these are placed separately at the bottom of the table in the f-block. The lanthanoid contraction also decrease the size of the elements of the third transition series (Hf onward). As a result, there is a negligible difference in the metallic radii of the second and third members in each group of transition metals.