1. why YbS and YbI2 are semiconducting solids but LaS and LaI2 show metallic character.
2. Why is aqueous solution of Eu2+ thermodynamically less susceptible to oxidation than any other aqueous M2+ lanthanides cations?
3. Why higher oxidation states are more common for actinides than for lanthanides?
4. Why are the lanthanides are endowed with the ability to remain as +3 cations in solution?
5. why are Actinides elements endowed with high tendency towards complex formation?