Compare the chemistry of the actinoids with that of lanthanoids with reference to:
$(i)$ electronic configuration
$(ii)$ oxidation states and
$(iii)$ chemical reactivity.

(A) Electronic configuration:
The general electronic configuration for lanthanoids is $[Xe]^{54} 4f^{0-14} 5d^{0-1} 6s^{2}$ and that for actinoids is $[Rn]^{86} 5f^{1-14} 6d^{0-1} 7s^{2}$. Unlike $4f$ orbitals,$5f$ orbitals are not deeply buried and participate in bonding to a greater extent.
Oxidation states:
The principal oxidation state of lanthanoids is $+3$. However,sometimes we also encounter oxidation states of $+2$ and $+4$ due to the extra stability of fully-filled and half-filled orbitals. Actinoids exhibit a greater range of oxidation states because the $5f, 6d,$ and $7s$ levels are of comparable energies. Again,$+3$ is the principal oxidation state for actinoids.
Chemical reactivity:
In the lanthanoid series,the earlier members are more reactive,with reactivity comparable to $Ca$. With an increase in atomic number,they behave similar to $Al$. Actinoids are highly reactive metals,especially when finely divided. When added to boiling water,they give a mixture of oxide and hydride. Actinoids combine with most non-metals at moderate temperatures. Alkalies have no action on them,and they are only slightly affected by nitric acid due to the formation of a protective oxide layer.