Question

Account for the following:

Zirconium (Zr) and Hafnium (Hf) are difficult to separate.

Answer 1

Zirconium (40) and hafnium (72) have the same size, possess similar characteristics and belong to the same group. These are found combined in natural minerals and are difficult to separate. As a result, lanthanide contraction makes it impossible to separate Zr and Hf.