Which of the following elements belongs to the actinoids?

Discuss the trends in oxidation states shown by actinoids.

State the $E^o$ values of lanthanoids and provide their reactions with the following: $(i)$ $H_2$,$(ii)$ Carbon,$(iii)$ Dilute acid,$(iv)$ Halogens,$(v)$ $O_2$,and $(vi)$ $H_2O$.

Identify the rare earth element from the following.

Identify the ion having $4f^6$ electronic configuration.

Provide the electronic configurations of lanthanoids $(4f)$ series elements $(Ln)$ and their ions $Ln^{2+}$ and $Ln^{3+}$,and state their characteristics.