Question

Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

Answer 1

The lanthanides that exhibit +2 and +4 states are shown in the given table. The atomic numbers of the elements are given in parentheses.

+2	+4
Nd (60)	Ce (58)
Sm (62)	Pr (59)
Eu (63)	Nd (60)
Tm (69)	Tb (65)
Yb (70)	Dy (66)

After forming Ce⁴⁺, Ce attains a stable electronic configuration of [Xe].

After forming Tb⁴⁺, Tb attains a stable electronic configuration of [Xe] 4f⁷.

After forming Eu²⁺, Eu attains a stable electronic configuration of [Xe] 4f⁷.

After forming Yb²⁺, Yb attains a stable electronic configuration of [Xe] 4f¹⁴.

Answer 2

All lanthanoids show the Ln³⁺ oxidation state. But some of them also show +2 and +4 states in solution and solid forms, such as Ce⁴⁺, Eu²⁺, Yb²⁺, Tb⁴⁺, etc. The changing oxidation state correlates with electronic configuration owing to the enhanced stability of half-filled, fully filled, or vacant orbitals. e.g., Ce⁴⁺ has 4f⁰, Eu²⁺ has 4f⁷, Tb⁴⁺ has 4f⁷, and Yb²⁺ has 4f1⁴ configuration.