Which of the following substances is ionic in nature?

Which of the following has the strongest bond?

Which of the following substances has the highest melting point?

Write Lewis symbols for the following atoms and ions:
$S$ and $S^{2-}$; $Al$ and $Al^{3+}$; $H$ and $H^{-}$

Which of the following is a favourable condition for the formation of an ionic bond?

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