Which of the following is an ionic compound?

Which of the following substances has the highest boiling point?

Ionic bonds are usually formed by the combination of elements with:

Among the bonds formed by a chlorine atom with atoms of hydrogen,chlorine,sodium,and carbon,the strongest bond is formed between:

The lattice energies of $KF$,$KCl$,$KBr$ and $KI$ follow the order:

Consider the Born-Haber cycle for the formation of an ionic compound given below and identify the compound $Z$ formed.
$M_{(s)}$ $\xrightarrow{\Delta H_1} M_{(g)}$ $\xrightarrow{\Delta H_2} M^{+}_{(g)}$
$\frac{1}{2} X_{2(g)}$ $\xrightarrow{\Delta H_3} X_{(g)}$ $\xrightarrow{\Delta H_4} X^{-}_{(g)}$
$M^{+}_{(g)} + X^{-}_{(g)} \xrightarrow{\Delta H_5} Z$