(N/A) The actinoids exhibit a greater range of oxidation states compared to the lanthanoids. This is because the $5f$,$6d$,and $7s$ energy levels are of comparable energies.
$1$. The dominant oxidation state of all actinoids is $+3$.
$2$. The early actinoids (like $Th$,$Pa$,$U$,$Np$,$Pu$) show a greater variety of oxidation states,such as $+4, +5, +6$,and even $+7$ for $Np$ and $Pu$.
$3$. As we move along the series,the $+3$ oxidation state becomes more stable due to the increasing effective nuclear charge and the contraction of the $5f$ orbitals.
$4$. The $+3$ oxidation state is the most stable state for the later actinoids.