Question

Q. 22. How would you account for the following?
(ii) Zr (Z = 40) and Hf (Z = 72) have almost identical radii

Answer 1

Dear student,
Zr and Hf have almost identical radii due to lanthanide contraction. Lanthanide contraction is a resultant of poor shieldinf of 4f electron. Due to this, 6s electron get attracted towards the nucleus resulting in the steady decrease in radii of elements.
4f electrons show poor shielding effect due to diffused shape of f orbital.
Regards.