Stabilization of the lowest oxidation states of lanthanides and actinides

Stabilization of the lowest oxidation states of actinides and lanthanides in different condensed media (solutions, melts, condensed clusters) is considered. Elements in the each of these families can be divided into two groups. In one of the group stabilization of the state 2+ is achieved in the account of participation of d-electron in chemical bond and in another one, where energy of stabilization of d-level is lower of the energy of fd-excitation of M2+ ion stabilization is proportional to fd-excitation energy