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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 is the physical process of giving or taking away electrons from an atom. That makes the atom into an ion, because ions have electrical charge.

In the process of ionization, an electrically neutral atom becomes either positively or negatively charged. Some substances are easier to ionize than others. This depends on the ionization energy. [1] Ionizing radiation is a common cause, but ionization can also be done artificially.


  1. Encyclopædia Britannica. Ionization (chemistry and physics). Encyclopedia Britannica Online, 13 May 2014. <>.