Question

(b) Write two consequences of lanthanide contraction.

Hint:

The lanthanide contraction accounts for many of the similarities in the properties of d-block and f-block elements, especially concerning ionic radii and chemical behavior.

Answer 1

Lanthanide contraction refers to the gradual reduction in the ionic radius of the lanthanide series as the atomic number increases, due to the ineffective shielding of the 4f-electrons. Two significant consequences of lanthanide contraction are: 1. Decreasing ionic radii: As the atomic number increases from \( La^{3+} \) to \( Lu^{3+} \), the size of the ions decreases. This results in a higher effective nuclear charge acting on the electrons, causing the ionic radii to shrink. 2. Similarity between 3d and 4d/5d elements: Lanthanide contraction creates similarities in the properties of the lanthanide elements and the d-block elements in the same period. For example, \( Zr \) (a 4d element) and \( Hf \) (a 5d element) exhibit very similar ionic radii due to this contraction. \bigskip Step 2: Thus, lanthanide contraction leads to smaller ionic radii and greater similarities in the properties of lanthanides and d-block elements. \bigskip