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

Lanthanoids exhibiting + 4 oxidation state : Cerium `(._(58)Ce)`, praseodymium `(._(59)Pr)`, Neodymium `(._(60)Nd)`, Terbium `(._(65)Tb)`, Dysprosium `(._(66)Dy)`. Lanthanoids exhibiting + 2 oxidation state : Neodymium `(._(60)Nd)`, Samarium `(._(62)Sm)`, Europium `(._(63)Eu)`, Thulium `(._(69)Tm)` and Ytterbium `(._(70)Yb)`. + 4 and + 2 oxidation states of teh above mentioned elements arises mainly from the extra stability of empty, half - filled and completely filled - subshell. For example, `Ce^(4+)` with `4f^(0)` arrangment has noble gas configuration. Similarly, `Eu^(2+)` and `Tb^(4+)` have `4f^(7)` configuration, while `Yb^(2+)` has `4f^(14)` configuration.