Ionic bonding — common mistakes

When explaining conductivity, always state what the charge carriers are (mobile ions) and why they are free to move (molten or dissolved state). For non-conductivity in solids, state that the ions are the potential charge carriers but are held in fixed positions within the lattice.

For a substance to conduct electricity, it must contain charged particles that are free to move. In solid sodium chloride, the Na⁺ and Cl⁻ ions are the charged particles, but they are held in fixed positions within the rigid giant ionic lattice and cannot move to carry a current.

No, ionic compounds like NaCl do not exist as discrete molecules. The formula 'NaCl' represents the empirical formula, which is the simplest 1:1 ratio of Na⁺ to Cl⁻ ions in the vast, continuous giant ionic lattice.

The strength of the electrostatic attraction, which is quantified by lattice energy. This attraction is strongest when the ions have high charges (e.g., 2+ and 2- are stronger than 1+ and 1-) and small ionic radii. This combination leads to a high charge density, pulling the ions together more tightly.

While the forces within the lattice are strong (high lattice energy), the attraction between the ions and polar water molecules can also be very strong. If the energy released when the ions are surrounded by water molecules (hydration enthalpy) is comparable to or greater than the lattice energy, the compound will dissolve.