As a result, the force of attraction between each electron and the nucleus of the other atom is larger than the force of repulsion between the two nuclei, as long as the nuclei are not brought too close together. The net result of pairing the electrons and placing them between the two nuclei is a system that is more stable than a pair of isolated atoms if the nuclei are close enough together to share the pair of electrons, but not so close that repulsion between the nuclei becomes too large. Removing an ion from this compound therefore involves breaking at least six bonds. Some of these bonds would have to be broken to melt NaCl, and they would all have to be broken to boil this compound. As a result, ionic compounds such as NaCl tend to have high melting points and boiling points.
Ionic compounds are therefore solids at room temperature.
Cl 2 consists of molecules in which one atom is tightly bound to another, as shown in the figure above. The covalent bonds within these molecules are at least as strong as an ionic bond, but we don't have to break these covalent bonds to separate one Cl 2 molecule from another. As a result, it is much easier to melt Cl 2 to form a liquid or boil it to form a gas, and Cl 2 is a gas at room temperature. The difference between ionic and covalent bonds also explains why aqueous solutions of ionic compounds conduct electricity, while aqueous solutions of covalent compounds do not. When a salt dissolves in water, the ions are released into solution.