Question

Consider the following statements
I. $La(OH{)}_3$ is least basic among hydroxides of lanthanides.
II. $Z{r}^{4+}$ and $H{f}^{4+}$ possess almost the same ionic radii.
III. $C{e}^{4+}$ can act as an oxidizing agent.
Which of the above is/are true?

• A. I and III
• B. II and III
• C. II only
• D. I and II

Answer 1

The correct option is B II and III

The ionic radii of $Z{r}^{4+}$ and $H{f}^{4+}$ are almost similar due to the lanthanide contraction which means the steady decrease in the size of the atoms with the increase from lanthanum through Lutetium due to the poor shielding of the $4f$ $e^{-}$, the $e^{-}$ pull towards the nucleus increases thereby decreasing the size.

$C{e}^{4+}$ act as oxidizing agent as it oxidizes other elements by itself getting reduced as $C{e}^{3+}$ is more stable than $C{e}^{4+}$ oxidation state so in order to attain stable $+3$ oxidation it gets reduced.

The basic characteristics of lanthanoid hydroxides decrease down the group.

Thus $La(OH{)}_3$ is the most basic.

Thus only statement II and III are correct.