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

The +4 oxidation state of cerium is not known in solution

The correct answer is (3) The +4 oxidation state of cerium is not known in solution

Cerium is an important member of the lanthanides, and it can have a variety of oxidation states. The most common oxidation states of cerium are +3 and +4. The +3 oxidation state is more stable than the +4 oxidation state, but the +4 oxidation state is still known in solution.

In solution, cerium (IV) is typically found as the cerium(IV) ion, Ce⁴⁺. Ce⁴⁺ is a strong oxidizing agent, and it can react with other compounds to give them a higher oxidation state. For example, Ce⁴⁺ can react with water to give cerium(III) hydroxide, Ce(OH)₃, and oxygen gas.

Therefore, statement (3) is incorrect. The +4 oxidation state of cerium is known in solution.

Here are some additional details about the oxidation states of cerium:

The +3 oxidation state of cerium is the most stable oxidation state. It is found in many cerium compounds, such as cerium(III) oxide, Ce₂O₃, and cerium(III) chloride, CeCl₃.

The +4 oxidation state of cerium is less stable than the +3 oxidation state. However, it is still known in solution, and it is found in some cerium compounds, such as cerium(IV) oxide, CeO₂, and cerium(IV) fluoride, CeF₄.

Cerium can also have other oxidation states, such as +2, +1, and +0. However, these oxidation states are less common than the +3 and +4 oxidation states.