The lanthanide contraction is responsible for the fact that
(a)Zr and Yt have about the same radius
(b)Zr and Nb have smaller oxidation state
(c)Zr and Hf have about the same radius
(d)Zr and Zn have the same oxidation state.

Options

A. `Zr` and `Y` have about the same radius
B. `Zr` and `Nb` have similar oxidation state
C. `Zr` and `Hf` have about the same radius
D. `Zr and Ce` have same oxidation state.

Answer

3

Explanation

The atomic radii of the second and third transition series are almost the same . This phenomenon is associated with the intervention of the `4f` orbitals which must be filled before the `5d` series of elements begin. The filling of `4f before 5d` orbital results in a regular decrease in atomic radii called Lanthanoid contraction which essentially compensates for the expected increase in atomic size with increasing atomic number . The net result of the lanthanoid contraction is that second and third d series exhibit similar radii `(e.g.,Zr 160)` pm, `Hf 159 pm)`