In which of the following compounds would the ionic radius of chromium be the smallest?

Which of the following elements has the maximum first ionization potential?

The number of unpaired electrons in $Cr^{3+}$ ion is

Which of the following is $NOT$ a physical or chemical characteristic of interstitial compounds?

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

Given below are two statements:
Statement $I$: Ferromagnetism is considered as an extreme form of paramagnetism.
Statement $II$: The number of unpaired electrons in a $Cr^{2+}$ ion $(Z=24)$ is the same as that of a $Nd^{3+}$ ion $(Z=60)$.
In the light of the above statements,choose the correct answer from the options given below: