Question

The CORRECT order of ionic radii of the following lanthanides is:

• A. Eu\(^{3+}\) $>$ Ce\(^{3+}\) $>$ Tb\(^{3+}\)
• B. Ce\(^{3+}\) $>$ Eu\(^{3+}\) $>$ Tb\(^{3+}\)
• C. Eu\(^{3+}\) = Ce\(^{3+}\) $>$ Tb\(^{3+}\)
• D. Eu\(^{3+}\) $>$ Ce\(^{3+}\) $>$ Tb\(^{3+}\)

Hint:

In lanthanides, ionic radii generally decrease across the series due to the increasing effective nuclear charge.

Answer 1

The Correct Option is B

The ionic radii of lanthanides follow a general trend where the ionic radii decrease as we move from left to right across the series.
- Ce\(^{3+}\) has the largest ionic radius among the three due to its position and electronic configuration in the 4f series.
- Eu\(^{3+}\) is next because of the effect of the 4f electron configuration, which leads to a smaller size compared to Ce\(^{3+}\).
- Tb\(^{3+}\) has the smallest ionic radius due to its higher nuclear charge and effective nuclear charge acting on the electrons.
Therefore, the correct order of ionic radii is: \[ \text{Ce}^{3+}>\text{Eu}^{3+}>\text{Tb}^{3+} \]