ionization

alt=The solar wind moving through the magnetosphere alters the movements of charged particles in the Earth's thermosphere or exosphere, and the resulting ionization of these particles causes them to emit light of varying colour, thus forming auroras near the polar regions.|thumb|201x201px|The solar wind moving through the [[magnetosphere alters the movements of charged particles in the Earth's thermosphere or exosphere, and the resulting ionization of these particles causes them to emit light of varying color, thus forming auroras near the polar regions.]] Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule is called an ion. Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules, electrons, positrons, protons, antiprotons, and ions, or through the interaction with electromagnetic radiation. Heterolytic bond cleavage and heterolytic substitution reactions can result in the formation of ion pairs. Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected.

==Uses== Everyday examples of gas ionization occur within a fluorescent lamp or other electrical discharge lamps. It is also used in radiation detectors such as the Geiger-Müller counter or the ionization chamber. The ionization process is widely used in a variety of equipment in fundamental science (e.g., mass spectrometry) and in medical treatment (e.g., radiation therapy). It is also widely used for air purification, though studies have shown harmful effects of this application.