The magnetic properties of the actinoids are more complex than those
of the lanthanoids Although the variation in the magnetic susceptibility
of the actinoids with the number of unpaired 5 f electrons is roughly
parallel to the corresponding results for the lanthanoids, the latter have
higher values It is evident from the behaviour of the actinoids that the ionisation
enthalpies of the early actinoids, though not accurately known, but are
lower than for the early lanthanoids This is quite reasonable since it is to
be expected that when 5f orbitals are beginning to be occupied, they will
penetrate less into the inner core of electrons