Question

Cerium (atomic number $=58$) is an important member of the lanthanoids. Which of the following statements about cerium is incorrect?

• A. The $+4$ oxidation state of cerium is not known in solutions.
• B. The $+3$ oxidation state of cerium is more stable than the $+4$ oxidation state.
• C. The common oxidation states of cerium are $+3$ and $+4$.
• D. Cerium (IV) acts as an oxidising agent.

Answer 1

Answer: (A)

The $+4$ oxidation state of cerium is not known in solutions.

Cerium is an important member of the lanthanoids. The electronic configuration of cerium is $\left[Xe\right]4f^{1}5d^{1}6s^2$.

Hence, the common oxidation states of cerium are $+3$ and $+4$.

However, the $+3$ oxidation state of cerium is more stable than the $+4$ oxidation state. Besides, cerium (IV) acts as an oxidising agent. Also, the $+4$ oxidation state of cerium is stable in solutions.

Hence, option A is incorrect.