The following factors facilitate the formation of an ionic bond between a metal and a non-metal :
(i) Ionization energy : Lesser the ionization energy, greater is the ease of formation of a cation.
(ii) Electron affinity : High electron affinity favours formation of an anion.
(iii) Lattice Energy : It is defined as the amount of energy released when cations and anions are brought close to each other from infinity to their respective equilibrium sites in the crystal lattice to form one mole of the ionic compound. The higher the magnitude of the lattice energy, the greater is the tendency of the formation of an ionic bond.