Final answer:
The most ionic compound among LiCl, NaCl, CsCl, and AlCl₃ is CsCl, due to the greater difference in electronegativity between Cs and Cl. The correct answer is option: c. CsCl,
Step-by-step explanation:
Among the options of LiCl, NaCl, CsCl, and AlCl₃, the most ionic compound would be CsCl. Ionic character increases with the difference in electronegativity between the bonded atoms.
Elements towards the bottom left of the periodic table (like Cs) are much less electronegative than elements towards the top right (like Cl), so there is a greater difference in electronegativity between Cs and Cl than between Li and Cl, Na and Cl, or Al and Cl.
Furthermore, since AlCl₃ contains a metal with a +3 charge, it has more covalent character due to polarization of the electron cloud around the chloride ions.