Question

All the following have nearly same size due to lanthanide contraction except (A) zr, Br (B) Mo, w (C) Nb, Ta (D) Y, La

Answer 1

Answer:

Zirconium(Zr) and Bromine(Br)

Explanation:

Zirconium and Hafnium(Hf) have same size.

Answer 2

Answer:

$\Large{\underline{\underline{\bf{Option\:A: \: Zr,\:Br}}}}$

Explanation:

$\dag$ This is because the size of the Zirconium atom is similar to that of Hafnium atom due to lanthanoid contraction and not to that of bromine atom.

$\dag$ The atomic radius of Zr is 160 pm and that of Hf is 159 pm which is almost similar.

$\Large{\underline{\underline{\bf{More\:information:}}}}$

$\dag$Lanthanoid contraction:

• The filling of 4f before 5d orbitals which results in the decrease in the    atomic radii is called as lanthanoid contraction.

$\dag$Factor responsible for lanthanoid contraction:

• The imperfect shielding of one electron by another in the same set of orbital is the reason for lanthanoid contraction. As a result the electrons experience effective nuclear charge and atomic radii gets reduced.

$\dag$Consequences of lanthanoid contraction:

• The lanthanoid contraction results in the similar atomic radii of of the second and third d series.
• They have very much similar physical and chemical properties which is much more than expected.
• It results in general increase in density of the elements.