question_answer 90)

  Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?

Answer:

                    Separation of Zr and Hf are quite difficult because of lanthanoid contraction. Due to lanthanoid contraction, they have almost same size (Zr = 160 pm and Hf = 159 pm) and thus, similar chemical properties. That's why it is very difficult to separate them by chemical methods.