Dissociation is the process by which a chemical combination breaks up into simpler constituents. Dissociation may be accomplished by the addition of energy, as in the case of gaseous molecules dissociated by heat; or by the action of a solvent on a polar compound (i.e., electrolytic decomposition). All electrolytes dissociate to some extent in polar solvents. The degree of dissociation can be used to calculate the equilibrium constant for the dissociation reaction.

In the case of diatomic molecules, the dissociation energy refers to the energy required to break the gaseous molecules into their constituent atoms. Generally, for families of molecules such as HF, HCl, HBr, and HI; or C₂, Si₂, and Pb₂, the heavier molecules tend to have smaller dissociation energies. In the case of N₂, O₂, and F₂, the dissociation energy increases with increasing net bonding. In general, there is an inverse relationship between dissociation energy...