Electrovalent compounds do not have

Which of the following is the correct order of lattice energy for the given ionic compounds?

$HCl$ gas is covalent and $NaCl$ is an ionic compound. This is because

If the enthalpy of sublimation of $Li$ is $155 \ kJ \ mol^{-1}$, enthalpy of dissociation of $F_2$ is $150 \ kJ \ mol^{-1}$, ionization enthalpy of $Li$ is $520 \ kJ \ mol^{-1}$, electron gain enthalpy of $F$ is $-313 \ kJ \ mol^{-1}$, and standard enthalpy of formation of $LiF$ is $-594 \ kJ \ mol^{-1}$, then the magnitude of the lattice enthalpy of $LiF$ is . . . . . . $kJ \ mol^{-1}$ (nearest integer).

The atomic numbers of the elements $X, Y, Z$ are $a, a+1, a+2$ respectively. $Z$ is an alkali metal. The nature of bonding in the compound formed by $X$ and $Z$ is

The electronic configurations of elements are $A = 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$ and $B = 1s^2 2s^2 2p^6 3s^2 3p^5$. Which of the following is the formula of the ionic compound that could be formed between these two elements $A$ and $B$?