Oxidation state of lanthanoids:
The common oxidation state of lanthanoids is +3. In addition to that some of the lanthanoids also show either +2 or +4 oxidation states.
Gd3+ and Lu3+ ions have extra stability, it is due to the fact that they have exactly half filled and completely filled f-orbitals respectively.their electronic c onfigurations are
Gd3+ : [ Xe ] 4 f 7
Lu3+ : [ Xe ] 4 f 14
Similarly Cerium and terbium attain 4f0 and 4f7 configurations respectively in the +4 oxidation states. Eu2+ and Yb2+ ions have exactly half filled and completely filled f orbitals respectively.
The stability of different oxidation states has an impact on the properties of these elements. the following table shows the different oxidation states of lanthanoids.