The lattice energy of CaF_2 is the energy change associated with which of the following processes?

• A. The formation of solid CaF_2 from gaseous Ca^{2+} and F^- ions
• B. The conversion of solid CaF_2 into its constituent elements in the gaseous state
• C. The dissolution of solid CaF_2 in water to form Ca^{2+} and F^- ions in solution
• D. The reaction of solid calcium with fluorine gas to form solid CaF_2

Answer: (A)

Verified step by step guidance

1. Understand that lattice energy is defined as the energy change when one mole of an ionic solid forms from its gaseous ions. It is a measure of the strength of the ionic bonds in the solid lattice.
2. Identify the process that involves the formation of the solid ionic compound from its gaseous ions. This means starting with gaseous cations and anions and ending with the solid lattice.
3. Review each option and determine which describes the formation of solid CaF_2 from gaseous Ca^{2+} and F^- ions. This corresponds to the lattice energy process.
4. Recognize that the other options describe different processes: decomposition into gaseous elements, dissolution in water, or direct reaction of elements, none of which define lattice energy.
5. Conclude that the lattice energy corresponds to the energy change when gaseous Ca^{2+} and F^- ions combine to form solid CaF_2.