Which of the following is least ionic?

Which of the following is generally true about ionic compounds?

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).

If an element in group $2$ forms a compound with an element in group $17$ of the periodic table,the compound formed is likely to

The most predominantly ionic compounds will be obtained from the combination of elements belonging to

Select the incorrect statement.