The correct order of atomic radii is

Which of the following has $6$ unpaired $f-$electrons?

Which element from the following lanthanoids has a half-filled $f$-orbital in its observed and expected electronic configuration?

The ionic radius of $La^{3+}$ is $1.06 \ \mathop{A}\limits^o$. Which of the following is the closest value for the ionic radius of $Lu^{3+}$ in $\mathop{A}\limits^o$? $(Lu = 71, La = 57)$

What are the elements of the $f$-block called?

The maximum number of possible oxidation states of actinoids are shown by