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

Explanation

`+4=_58Ce,_59Pr,_60Nd_65Tb,_66Dy`
` +2=_60Nd,_62Sm,_63Eu_65Tm,_66Yb`
`+2` oxidation state is exhibited when the lanthanoid has the configuration `5d^(0)6s^(2)` so that`2` electrons are easily lost,+4 oxidation state is exhibited when the configuration left is close to `4f^(0)(e.g.4g^(0).4f^(1),4f^(1))` or close to `4f^(7) (e.g.4f^(7) or 4f^(8)`