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Question
Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?
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Solution
As an effect of lanthanoid contraction, zirconium and hafnium have similar radius of 160 pm and 159 pm respectively. Due to this similarity in their size, they show similar physical and chemical properties.
Lanthanoid contraction: Because the elements in Row 3 have 4f electrons. These electrons do not shield good, causing a greater nuclear charge. This greater nuclear charge has a greater pull on the electrons and result in the decrease in their size and atomic radii.
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