Anhydrous aluminium chloride $(Al_2Cl_6)$ is a covalent compound and soluble in water,giving:

In the Born-Haber cycle for the formation of solid common salt $(NaCl)$,the largest contribution to the stability of the crystal lattice comes from:

Ionic compounds do not have

Use the following data to calculate $\Delta _{lattice}H^{\theta }$ for $NaBr$. $\Delta _{sub}H^{\theta }$ for sodium metal $= 108.4 \ kJ \ mol^{-1}$,ionization enthalpy of sodium $= 496 \ kJ \ mol^{-1}$,electron gain enthalpy of bromine $= -325 \ kJ \ mol^{-1}$,bond dissociation enthalpy of bromine $= 192 \ kJ \ mol^{-1}$,$\Delta _{f}H^{\theta }$ for $NaBr_{(s)}$ $= -360.1 \ kJ \ mol^{-1}$.

An atom of an element $A$ has three electrons in its outermost shell and that of $B$ has six electrons in the outermost shell. The formula of the compound between these two will be

Magnesium reacts with an element $(X)$ to form an ionic compound. If the ground state electronic configuration of $(X)$ is $1s^{2} 2s^{2} 2p^{3},$ the simplest formula for this compound is