Name the member of the lanthanoids series which exhibit +4 oxidation states and those which exhibit +2 oxidation state. Try to correlate this types of behavior with the electronic configuration of these elements.

Explanation

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

Ce after forming `Ce^(4+)` attains a stable electronic configuration of [Xe].
Tb after forming `Tb^(4+)` attains a stable electronic configuration of [Xe] `4f^(7)`.
Eu after forming `Eu^(2+)` attains a stable electronic configuration of `[Xe] 4f^(7)`.
Yb after forming `Yb^(2+)` attains a stable electronic configuration of [Xe] `4f^(14)`.