An increase in both atomic and ionic radii with atomic number occurs in any group of the periodic table and in accordance with this the ionic radii of Ti(IV) and Zr (IV) ions are `0.68 A^(@)` and `0.74 A^(@)` respectively , but for Hf(IV) ion, the ionic radius is `0.75 A^(@)` , which is almost the same as that for Zr(IV) ion . This is due to

Options

A. Greater degree of covalency in compounds of `Hf^(4+)`
B. Lanthanide contraction
C. Actinide contraction
D. Difference in co-ordinates nubmer of `Zr^(4+)` and `Hf^(4+)` in their compounds

Answer

B