AIEEE 2005 Chemistry Solved Paper

In the entire d-block,
Only in group 3, the size increase from top to bottom due to increase of no of shells in an atom. That is why size of Sc<Y<La. And shell size in group 3 is 3d<4d<5d.

But from group 4 to 12 , the size of 3d<4d but 4d≅5d due to lanthanide contraction. That is why Zr and Hf have about the same radius.