Energy released when gaseous ions form an ionic solid.

• A. Bond energy
• B. Activation energy
• C. Ionization energy
• D. Lattice energy

Answer: (D)

Lattice energy is the energy released when gaseous ions come together to form an ionic solid. This release happens because the ions arrange themselves in a crystal to maximize attractive forces between oppositely charged ions, lowering the system’s potential energy. The magnitude of this energy depends on the charges and sizes of the ions: higher charges and smaller ions produce stronger electrostatic attractions and thus a larger energy release.

This idea is often connected with the Born–Haber cycle, which links lattice energy to other steps in forming ionic compounds, helping explain why compounds with highly charged, small ions have large lattice energies and high melting points. It’s a different concept from bond energy (energy to break covalent bonds), activation energy (the energy barrier of a reaction), or ionization energy (energy to remove electrons to form ions).