Question

Most common oxidation state of Cerium (Ce) is:

• A. +3, +4
• B. +2, +3
• C. +2, +4
• D. +3, +5

Answer 1

The correct option is A +3, +4

Electronic configuration of Cerium is,$\left[Xe\right]4f^{1}5d^{1}6s^2$
Thus, its most stable oxidation state is +3 but +4 is also exist because it is favoured by its noble gas configuration.
$C{e}^{4+}$ revert back to common +3 oxidation state in slow rate. Hence, it used as strong oxidising agent in analytical method.