NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (a) The lattice energies of NaCl and KF are given in Table 8.1. Based on the lattice energies, would you expect the Na─Cl or the K─F distance to be longer?

Key Concepts

Lattice Energy

Lattice energy is the amount of energy released when gaseous ions combine to form an ionic solid. It is a measure of the strength of the forces between the ions in an ionic compound. Higher lattice energy indicates stronger ionic bonds, which typically results in shorter distances between cations and anions.

Ionic Radius

Ionic radius refers to the size of an ion in a crystal lattice. Cations are smaller than their parent atoms due to the loss of electrons, while anions are larger due to the gain of electrons. The size of the ions affects the distance between them in the lattice structure, influencing the overall lattice energy.

Coulomb's Law

Coulomb's Law describes the electrostatic interaction between charged particles. It states that the force between two charged ions is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. This principle helps explain how the distance between ions affects lattice energy and stability.