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Question
How would you account for the following?
Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
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Solution
This is because the atomic radii of 4d and 5d transition elements are nearly same. This similarity in size is consequence of lanthanide contraction. Because of this lanthanide contraction the radii of Hf becomes nearly equal to that of Zr.
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