The lanthanoid that would show color is

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.

Arrange the ions $Ce^{3+}$,$La^{3+}$,$Pm^{3+}$,and $Yb^{3+}$ in the increasing order of their ionic radii.

Which of the following forms a stable $+4$ oxidation state?

The highest oxidation state in plutonium (At. No. = $94$) is

Identify the correct decreasing order of ionic radii of the following lanthanoids: $Ce^{3+}$,$Pm^{3+}$,$Sm^{3+}$,and $Gd^{3+}$.