Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because___________.

Due to lanthanide contraction, the f electrons shield very poorly which leads to an increase in effective nuclear charge and hence a contraction in size. So, the atomic radii of Zirconium and Hafnium are very similar and therefore they have similar physical and chemical properties.