$Zr$ $(Z=40)$ and $Hf$ $(Z=72)$ have similar atomic and ionic radii because of :

The $E^{\Theta} (M^{2+} / M)$ value for copper is positive $(+0.34 \ V)$. What is the possible reason for this? (Hint: consider its high $\Delta_{a} H^{\Theta}$ and low $\Delta_{hyd} H^{\Theta}$)

Which of the following is not a representative element?

The general electronic configuration of transition elements is

What is the correct order of the theoretical magnetic moment for $Mn^{2+}$,$Cr^{2+}$,and $V^{2+}$?

Consider the following pairs of elements and identify the pairs of elements which have nearly same atomic radius.
$I$. $Y, La$
$II$. $Zr, Hf$
$III$. $Mo, W$
$IV$. $Cr, Mo$