Question

Name a member of the lanthanoid series
(I) which exhibits +4 oxidation state
(II) which exhibits +2 oxidation state.

Hint:

Lanthanoid oxidation states are driven by the stability of empty (\(f^0\)), half-filled (\(f^7\)), and completely filled (\(f^{14}\)) f-subshells.

Answer 1

(I) Member of the lanthanoid series exhibiting +4 oxidation state:
A member of the lanthanoid series that exhibits the +4 oxidation state is cerium (Ce). Cerium is unique among the lanthanides because it can easily exist in two oxidation states: +3 and +4. The +4 oxidation state is particularly stable for cerium when it has the electronic configuration \( 4f^0 \), indicating no electrons in the 4f orbitals. This makes cerium a highly oxidizing element in its +4 state. In this oxidation state, cerium behaves as a strong oxidizing agent, and its compounds are typically yellow in color. Cerium(IV) compounds are used in various applications, including catalysts and in the preparation of glass and ceramics.
(II) Member of the lanthanoid series exhibiting +2 oxidation state:
A member of the lanthanoid series that exhibits the +2 oxidation state is europium (Eu). Europium is notable because, like cerium, it can exist in multiple oxidation states. The +2 oxidation state of europium has the electronic configuration \( 4f^7 \), which is stable due to the half-filled nature of the 4f orbital, making europium in this state relatively stable and less reactive compared to other lanthanides. Europium(II) compounds are typically used as phosphors in fluorescent lamps and in some types of laser technology. The +2 oxidation state of europium is relatively rare among the lanthanides, and europium(II) salts are often highly reducing agents.