Chemistry - f-block Question with Solution | TestHub

Question Explanation:

Find the decreasing order of atomic radii.

Concept:

This question is based on Lanthanide Contraction.

Solution:

As the atomic number increases across the lanthanide series, the atomic and ionic radii generally decrease due to poor shielding by 4f electrons, a phenomenon known as lanthanide contraction. However, Europium (Eu) has an exceptionally large atomic radius due to its stable half-filled f-orbital configuration, which leads to weak metallic bonding.

General trend: Ce > Gd > Lu.

Due to its 4f⁷configuration, Eu has an unusually large size.

The correct order is Eu > Ce > Gd > Lu.