Latticeenergia

Lattice energy, or lattice enthalpy, is the energy required to convert one mole of a crystalline ionic solid into gaseous ions, A+(g) and B−(g). It is the endothermic step in the dissociation of the solid and is typically reported as a positive quantity in thermochemical data, although some contexts use the magnitude or the negative of this value when discussing formation from gaseous ions.

Lattice energy depends strongly on the charges of the ions and on their sizes. Higher ionic charges and smaller ion radii increase the electrostatic attraction that holds the lattice together, producing a larger lattice energy. The arrangement of ions in the crystal, summarized by the Madelung constant, also influences the strength of the lattice. Consequently, compounds with multiply charged ions or small ions tend to have substantially larger lattice energies than those with monovalent, larger ions. Across a period, lattice energy generally decreases down a group as ionic radii increase.

Methods and approximations: experimental lattice energies can be derived from the Born-Haber cycle, using measured enthalpies of formation, atomization, ionization, and electron affinity. Theoretically, the Born-Lande equation provides a framework based on ionic charges, radii, and the Madelung constant. Practical estimates often employ the Kapustinskii equation, which yields approximate lattice energies for ionic compounds without requiring detailed structural constants.

Lattice energy is a key factor in the stability of ionic solids, influencing melting points, solubility, and dissolution energetics. It helps explain trends in properties among salts and informs models of solid-state and solution-phase behavior.