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

`+4= ._(58)Ce, ._(59)Pr, ._(60)Nd, ._(65)Tb, . _(66)Dy`, `+2 = ._(60)Nd, ._(62)Sm, ._(63)Eu, . _(69) Tm, ._(70)Yb`
`+2` oxidation state is exhibited when the configuration left is close is to `4f^(0) (e.g., 4f^(0), 4f^(1), 4f^(2))` or close to `4f^(7) ( e.g., 4f^(7) ` or `4f^(8))`