Question

Because of lanthanoid contraction, which of the following
pairs of elements have nearly same atomic radii ? (Numbers
in the parenthesis are atomic numbers). [2015]
(a) Zr (40) and Nb (41) (b) Zr (40) and Hf (72)
(c) Zr (40) and Ta (73) (d) Ti (22) and Zr (40)

Answer 1

Because of lanthanoid contraction Zr (40) and Hf (72) have nearly same atomic radii. So option B is correct.

Explanation:

Atomic radii:

It is the average distance from nucleus of an atom to outer most electronic shell or valance shell.

Because of lanthanoid contraction Zr (40) and Hf (72) have nearly same atomic radii.

Element       atomic radii (pm)

Zr                   155

Hf                   155

Ta                    145

Ti                     140

Nb                   145