Question

(b) Write two consequences of lanthanide contraction.

Hint:

The lanthanide contraction explains many similarities between the properties of d-block and f-block elements, particularly in terms of ionic radii and chemical behavior.

Answer 1

 Step 1: Lanthanide contraction refers to the gradual decrease in the ionic radius of the lanthanide series as the atomic number increases, caused by the poor shielding effect of the 4f-electrons. Two important 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, leading to an increase in the effective nuclear charge experienced by the electrons. This results in a decrease in the ionic radii. 2. Similarity between the 3d and 4d/5d elements: The lanthanide contraction leads to 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) have very similar ionic radii due to the lanthanide contraction. 

 Step 2: Thus, the lanthanide contraction results in smaller ionic radii and increased similarities between the properties of lanthanides and d-block elements.