LATTICE ENERGY

amount of energy released when gaseous ions are brought together from infinite separation to form a crystal. For each particular solid, the lattice energy is a constant that measures how tightly the constituent particles are held together. The lattice energy can be calculated if the arrangement and spacing of the particles are known. The attractive forces between oppositely charged ions make a large negative contribution to the lattice energy of ionic solids, such as common table salt, and the repulsive forces between similarly charged ions make a small positive contribution. Typical values for lattice energies of ionic solids at room temperature are roughly -200 kilocalories per mole.