Иондық кристалдардың түзілу энергиясы

Energy change upon the formation of one mole of ionic solid

In chemistry, the lattice energy is the energy change upon formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to initially be in the gaseous state. It is a measure of the cohesive forces that bind ionic solids. The size of the lattice energy is connected to many other physical properties including solubility, hardness, and volatility. Since it generally cannot be measured directly, the lattice energy is usually deduced from experimental data via the Born–Haber cycle.

The lattice energy of an ionic compound depends strongly upon the charges of the ions that comprise the solid, which must attract or repel one another via Coulomb's Law. More subtly, the relative and absolute sizes of the ions influence London dispersion forces also exist between ions and contribute to the lattice energy via polarization effects. For ionic compounds made of molecular cations and/or anions, there may also be ion dipole and dipole dipole interactions if either molecule has a molecular dipole moment. The theoretical treatments described below are focused on compounds made of atomic cations and anions, and neglect contributions to the internal energy of the lattice from thermalized lattice vibrations.

The following table presents a list of lattice energies for some common compounds as well as their structure type. Compound Experimental Lattice Energy Structure type Comment LiF −1030 kJ/mol NaCl difference vs. sodium chloride due to greater charge/radius for both cation and anion NaCl −786 kJ/mol NaCl reference compound for NaCl lattice NaBr −747 kJ/mol NaCl weaker lattice vs. NaCl NaI −704 kJ/mol NaCl weaker lattice vs. NaBr, soluble in acetone CsCl −657 kJ/mol CsCl reference compound for CsCl lattice CsBr −632 kJ/mol CsCl trend vs CsCl like NaCl vs. NaBr CsI −600 kJ/mol CsCl trend vs CsCl like NaCl vs. NaI MgO −3795 kJ/mol NaCl M2+O2 materials have high lattice energies vs. M+O−. MgO is insoluble in all solvents CaO −3414 kJ/mol NaCl M2+O2 materials have high lattice energies vs. M+O−. CaO is insoluble in all solvents SrO −3217 kJ/mol NaCl M2+O2 materials have high lattice energies vs. M+O−. SrO is insoluble in all solvents MgF2 −2922 kJ/mol rutile contrast with Mg2+O2 TiO2 −12150 kJ/mol rutile TiO2 (rutile) and some other M4+(O2 )2 compounds are refractory materials