Compare the chemistry of actinoids with that of the lanthanoids with special reference to:
$(i)$ electronic configuration
$(ii)$ atomic and ionic sizes
$(iii)$ oxidation state
$(iv)$ chemical reactivity.

(N/A) $(i)$ Electronic configuration: The general electronic configuration for lanthanoids is $[Xe] \ 4f^{0-14} \ 5d^{0-1} \ 6s^2$ and that for actinoids is $[Rn] \ 5f^{1-14} \ 6d^{0-1} \ 7s^2$. Unlike $4f$ orbitals,$5f$ orbitals are not deeply buried and participate in bonding to a greater extent.
$(ii)$ Atomic and ionic sizes: Similar to lanthanoid contraction,actinoids exhibit actinoid contraction (overall decrease in atomic and ionic radii). The contraction is greater in actinoids due to the poorer shielding effect of $5f$ orbitals compared to $4f$ orbitals.
$(iii)$ Oxidation states: The principal oxidation state of lanthanoids is $+3$. However,$+2$ and $+4$ states are also observed due to the stability of empty,half-filled,or fully-filled $f$-orbitals. Actinoids exhibit a greater range of oxidation states (e.g.,$+3, +4, +5, +6, +7$) because the $5f, 6d,$ and $7s$ energy levels are of comparable energies.
$(iv)$ Chemical reactivity: Lanthanoids are highly reactive,similar to calcium,but reactivity decreases with increasing atomic number. Actinoids are highly reactive metals,especially when finely divided. They react with boiling water to form oxides and hydrides and combine with most non-metals at moderate temperatures. They are generally unaffected by alkalies,and their reaction with nitric acid is limited due to the formation of a protective oxide layer.