JEE Main · 2005 · 08 May 2005 · Offline · d and f Block Elements

The lanthanide contraction is responsible for the fact that

(A)Zr and Y have about the same radius state
(B)Zr and Nb have similar oxidation
(C)Zr and Hf have about the same radius✓ Correct
(D)Zr and Zn have the same oxidation

Answer: (C)

Solution

The lanthanide contraction is the steady shrinkage of size across the

4 f

series, caused by the feeble shielding those

4 f

electrons provide. Its consequence for the metals below is that the size increase expected on moving from the second to the third transition series is almost exactly cancelled. Zirconium and hafnium, one above the other in the same group, therefore end up with nearly identical atomic radii, which is why the two are so alike and so hard to tell apart.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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