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Question:

Because of lanthanoid contraction, which of the following pairs of elements have nearly the same atomic radii?

Zr (40) and Nb (41)

Zr (40) and Ta (73)

Ti (22) and Zr (40)

Zr (40) and Hf (72)

Solution:

Because of lanthanoid contraction, Zr(40) and Hf(72) have nearly the same atomic radii. Element Radius (ppm) Zr (40) 145 Hf (72) 144 Ta (73) 134 Ti (22) 132 Nb (41) 134 Hence, option A is correct.