Which of the following lanthanoid ions is diamagnetic?
(At. nos. $Ce = 58, Sm = 62, Eu = 63, Yb = 70$)

Identify the correct statements about lanthanoids:
$I$. $Ce^{4+}$ and $Tb^{4+}$ act as oxidising agents.
$II$. $Eu^{2+}$ and $Yb^{2+}$ act as reducing agents.
$III$. Mischmetal is an alloy of $95 \%$ lanthanoid metal and $5 \%$ iron.
$IV$. $La^{3+}$ and $Ce^{4+}$ are diamagnetic in nature.

The $f$ orbitals are half-filled and completely filled,respectively,in which of the following lanthanide ions?
(Given: Atomic numbers: $Eu=63, Sm=62, Tm=69, Tb=65, Yb=70, Dy=66$)

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 strongest base from the following.

If the ionic radius of $_{57}La^{3+}$ is $1.06 \ \mathring{A}$,then the ionic radius of $_{71}Lu^{3+}$ will be approximately close to which of the following values in $\mathring{A}$?