The correct order of the first ionization enthalpies is:

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 $\Delta_{hyd} H^{\Theta}$)

The increase in the atomic radii of the third $(5d)$ series of transition elements is very small,which may be accounted for by the filling of '$X$' orbitals before '$Y$' orbitals. $X$ and $Y$ are:

The electronic configuration of Gadolinium ($Gd$,$Z = 64$) is:

Which of the following oxides has the maximum basicity?

For the transition elements $Cr, Mn, Fe,$ and $Co$,the correct order of the negative values of $E^o_{M^{2+}/M}$ is: