Which of the following statements is correct regarding the first $(I)$ and second $(II)$ ionization enthalpies of sodium $(Na)$ and magnesium $(Mg)$?

For $Mg$,the values of $\Delta_iH_1$ and $\Delta_iH_2$ are $178 \, kcal \, mol^{-1}$ and $348 \, kcal \, mol^{-1}$ respectively. The enthalpy change for the reaction $Mg \to Mg^{2+} + 2e^-$ is ............. $kcal \, mol^{-1}$.

The first four $I.E.$ values of an element are $284, 412, 656$ and $3210 \ kJ \ mol^{-1}$. The number of valence electrons in the element are

The first ionization enthalpies of four consecutive elements present in the second period of the periodic table are $8.3, 11.3, 14.5$ and $13.6 \ eV,$ respectively. Which one of the following is the first ionization enthalpy of nitrogen?

Which of the following is the incorrect order of ionisation energy $(I.E.)$?

Which of the following orders regarding ionization energy is correct?