Which orbitals,$4f$ or $5f$,are more capable of participating in bond formation?

The correct order of ionic radii of $Ce$,$La$,$Pm$ and $Yb$ in $+3$ oxidation state is

Identify the isoelectronic pair of ions from the following.

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ Actinoid contraction is greater than lanthanoid contraction.
$(b)$ Actinoids are elements of the $4f$ series.
$(c)$ All actinoid elements have a $7s^2$ configuration.

Which of the following is not a consequence of the Lanthanoid contraction?

Consider the following two statements:
$Statement-I:$ Among $Mg, Al, Mg^{2+}, Al^{3+}$,the one having the smallest size is $Al^{3+}$.
$Statement-II:$ $Eu$ has an exceptionally high atomic radius among lanthanide elements.
The correct answer is: