
(i) Electronic configuration
The general electronic configuration for lanthanoids is [Xe]544f0-145d0-16s2 and that of actinoids is [Rn]865f1-146d0-17s2. Unlike 4f orbitals, the 5f orbitals are not deeply buried and participate in bonding to a greater extent.
(ii) Oxidation states
The usual oxidation state of lanthanoids is (+3). Also encounter oxidation states of + 2 and + 4 are seen rarely. This is because of extra stability of fully-filled and half-filled orbitals. Actinoids exhibit a greater range of oxidation states. This is because the 5f, 6d, and 7s levels are all f comparable energies. Like lanthanoids, (+3) is also the principal oxidation state for actinoids.
(iii) Chemical reactivity
In the lanthanide series, the elements present at the beginning of the periods are more reactive. With an increase in the atomic number, the reactivity of lanthanides decreases.
Actinoids, on the other hand, are highly reactive metals. Actinoids combine with most of the non-metals at moderate temperatures. Alkalies have no action on these actinoids. In case of acids, they are slightly affected by nitric acid due to the formation of a protective oxide layer.