<P> Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions , often in conjunction with other chemical changes . Ionization can result from the loss of an electron after collisions with subatomic particles , collisions with other atoms , molecules and ions , or through the interaction with light . 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 . </P>
what changes when an ion forms from an atom or when an atom forms from an ion
acquires a negative or positive charge by gaining or losing electrons