# You have three substances: "lithium fluoride"; "carbon dioxide"; and "dinitrogen pentoxide". Which species should have the highest melting and boiling point?

Ionic substances are intrinsically non-molecular, and (usually) exhibit exceptionally high melting and boiling points. And thus $\text{lithium fluoride}$, $i . e . L {i}^{+} {F}^{-}$, an ionic substance, with no discrete molecules, should have much higher melting and boiling points than MOLECULAR $C {O}_{2}$, and ${N}_{2} {O}_{5}$.