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.
Among the lanthanoid series, the members that exhibit +4 oxidation state include Cerium (Z = 58), which is well known to exhibit this oxidation state.
The members exhibiting +2 oxidation state are those lanthanoids which can attain relatively stable electronic configurations by retaining or achieving favourable f-orbital arrangements.
The correlation with electronic configurations is significant. As discussed in the context regarding actinoids, the 5f, 6d and 7s levels are of comparable energies, which allows for a greater range of oxidation states. A similar principle applies to lanthanoids where the energies of 4f, 5d and 6s orbitals influence the oxidation states exhibited.
The tendency to exhibit +4 or +2 oxidation states depends on whether such oxidation states lead to stable electronic configurations. Elements favour oxidation states that result in stable f-orbital arrangements, similar to how actinoids show varied oxidation states based on their electronic configurations and comparable orbital energies.
Explanation
The context explicitly mentions Cerium (Z=58) as exhibiting +4 oxidation state in Example 4.10. The electronic configuration correlation is derived from the discussion about actinoids having comparable energies for 5f, 6d, and 7s levels, which allows varied oxidation states. A similar principle applies to lanthanoids. The context does not provide a complete list of all lanthanoids with +4 and +2 oxidation states, but the general principle of electronic configuration stability and comparable orbital energies explains this behaviour.