In which of the following compounds is the ratio of the size of the anion to the cation the smallest?

The Born-Haber cycle for $KCl$ is evaluated with the following data:
$\Delta_{f} H^{\ominus}$ for $KCl = -436.7 \ kJ \ mol^{-1}$
$\Delta_{sub} H^{\ominus}$ for $K = 89.2 \ kJ \ mol^{-1}$
$\Delta_{ionization} H^{\ominus}$ for $K = 419.0 \ kJ \ mol^{-1}$
$\Delta_{electron \ gain} H^{\ominus}$ for $Cl_{(g)} = -348.6 \ kJ \ mol^{-1}$
$\Delta_{bond} H^{\ominus}$ for $Cl_2 = 243.0 \ kJ \ mol^{-1}$
The magnitude of lattice enthalpy of $KCl$ in $kJ \ mol^{-1}$ is ..... . (Nearest integer)

For ionic solids,choose the correct option using $T$ (True) or $F$ (False) for the following statements:
$(1)$ They have very high melting and boiling points.
$(2)$ They are electrolytes.
$(3)$ They possess directional bond characteristics.
$(4)$ They can have isomorphic types of structures.

Write the favourable factors for the formation of ionic bond.

Which type of compounds show high melting and boiling points?

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