Which of the following statements is correct for $CsBr_3$?

Ionic compounds are formed most easily with

$AB$ is an ionic solid. The ionic radii of $A^{+}$ and $B^{-}$ are respectively $r_c$ and $r_a$. Lattice energy of $AB$ is proportional to:

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 $NaBr_{(s)}$ $= -360.1 \ kJ \ mol^{-1}$.

Amongst sodium halides $(NaF, NaCl, NaBr, NaI)$,$NaF$ has the highest melting point because of:

Anhydrous $AlCl_3$ is covalent; however,when it is dissolved in water,hydrated ionic species are formed. This transformation is owing to