∞ generated and posted on 2016.01.14 ∞
Gain or loss of an electron by an atom or molecule.
The consequence of ionization is the formation of an ion, though ions can also be further ionized. Note the similarity to the concepts of oxidation and reduction, which are loss and the gain of electrons, respectively. Ionization, however, must result in a full charge becoming associated with the substance being ionized.
Ionization is not the equivalent of dissociation and this is true for two reasons. First, dissociation represents the separation of two ions, that is, the ionization event has already occurred prior to the dissociation event. Second, ions can form also by gaining elections, i.e., not just by losing one or more electrons. Ionization thus can occur also in the course of "association" of electrons with atoms, not just the converse.