Why do Zr and Hf exhibit similar properties?
Answer: Lanthanoid contraction makes their atomic radii almost identical — same size + same group ⇒ nearly identical chemistry.
Solution
Hf lies immediately after the lanthanoids; the lanthanoid contraction cancels the normal size increase, so Zr (4d) and Hf (5d) have almost identical atomic and ionic radii (160 pm/159 pm).
With the same group configuration and the same size, their chemical properties are nearly indistinguishable (they always occur together).
With the same group configuration and the same size, their chemical properties are nearly indistinguishable (they always occur together).
CBSE Class 12 Board · 2001 · All India · Subjective