Physicists use lattice enthalpy to measure the strength of ionic solid forces. It is also called lattice energy. The enthalpy is expressed as a downward arrow.
The lattice enthalpy of aluminum oxide is -14,780kJ mol-1. It can be calculated by the Born-Haber cycle. This is a good way to evaluate the purity of ionic crystals.
The lattice enthalpy changes as an ion moves from the gaseous state to the solid. It is important to understand that the enthalpy change does not occur when the ion is scattered. The enthalpy changes are based on the distance between the centres of oppositely charged ions. The closer the ions are to each other in the lattice, the stronger the attraction.
When two moles of Al3+ ions are separated from each other in the gaseous state, they react with three moles of O2- ions. The resulting salt is produced. It is used as a tunnel barrier in superconducting devices. It is also used as a substrate for integrated circuits. It is also a catalyst support for many industrial catalysts.
The bond energy of O2 is 494 kj/mol. The ionization energies of aluminium are 578 kj/mol. It is also important to remember that the electron affinities of oxygen are -141 kj/mol. This can be reviewed by following this link.
When the ions are scattered, they are far apart, so there is not much attraction between them. The size of the ions is also a factor. Larger ions have a higher ionic solid lattice energy.