Ionization, in general, occurs whenever sufficiently energetic charged particles or radiant energy travel through gases, liquids, or solids. Charged particles, such as alpha particles and electrons from radioactive materials, cause extensive ionization along their paths.

How does an atom become ionized?

Ionization is the process by which ions are formed by gain or loss of an electron from an atom or molecule. If an atom or molecule gains an electron, it becomes negatively charged (an anion), and if it loses an electron, it becomes positively charged (a cation). Energy may be lost or gained in the formation of an ion.

What are the two ways to cause ionization?

Ionization can be induced by high energy radiation such as x rays and ultraviolet light (photoionization), bombardment by high energy electrons (electron impact ionization) or small molecular ions (chemical ionization) and by exposure to high electric fields (field ionization).