Which of the following statements are true?

A. Unlike Ga that has a very high melting point, Cs has a very low melting point.

B. On Pauling scale, the electronegativity values of N and Cl are not the same.

C. $\mathrm{Ar}, \mathrm{K}^{+}, \mathrm{Cl}^{-}, \mathrm{Ca}^{2+}$, and $\mathrm{S}^{2-}$ are all isoelectronic species.

D. The correct order of the first ionization enthalpies of $\mathrm{Na}, \mathrm{Mg}, \mathrm{Al}$, and Si is $\mathrm{Si}>\mathrm{Al}>\mathrm{Mg}>\mathrm{Na}$.

E. The atomic radius of Cs is greater than that of Li and Rb.

Choose the correct answer from the options given below :

The standard heat of formation, in $\mathrm{kcal} / \mathrm{mol}$ of $\mathrm{Ba}^{2+}$ is : [Given : standard heat of formation of $\mathrm{SO}_4^{2-}$ ion $(\mathrm{aq})=-216 \mathrm{kcal} / \mathrm{mol}$, standard heat of crystallisation of $\mathrm{BaSO}_4(\mathrm{~s})=-4.5 \mathrm{kcal} / \mathrm{mol}$, standard heat of formation of $\left.\mathrm{BaSO}_4(\mathrm{~s})=-349 \mathrm{kcal} / \mathrm{mol}\right]$

Match List-I with List-II

Choose the correct answer from the options given below:

$\mathrm{C}(\mathrm{s})+2 \mathrm{H}_2(\mathrm{~g}) \rightarrow \mathrm{CH}_4(\mathrm{~g}) ; \Delta \mathrm{H}=-74.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Which of the following diagrams gives an accurate representation of the above reaction? [ $\mathrm{R} \rightarrow$ reactants; $\mathrm{P} \rightarrow$ products]