d- and f-Block Elements: Lanthanide contraction MCQ

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Lanthanide contractionMediumQuestion 860006

Question

Lanthanide contraction causes Zr and Hf to have:

A
Nearly identical atomic radii and properties
Correct
B
Very different radii
C
Different oxidation states
D
Hf to be more reactive than Zr

Correct answer

Nearly identical atomic radii and properties

Explanation

Lanthanide contraction: the 14 lanthanides (4f filling) cause a gradual size decrease. By the time we reach 5d transition metals (Hf, Ta, W...), their radii are nearly equal to the 4d counterparts (Zr, Nb, Mo...). Zr and Hf have almost identical radii → very similar chemistry → hardest pair to separate.

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