Which of the following compounds has the lowest melting point?

Which of the following is not correct regarding the properties of ionic compounds?

The ionic bonds $X^{+}Y^{-}$ are formed when
$I$. electron affinity of $Y$ is high
$II$. ionization energy of $X$ is low
$III$. lattice energy of $XY$ is high
$IV$. lattice energy of $XY$ is low
Choose the correct code.

Which of the following compounds is the least ionic?

In the formation of $NaCl$ from $Na$ and $Cl$,which of the following occurs?

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