Ionization energy refers to the type and amount of energy required to cause a state of ionization. There are various different types of energy which are capable of producing an ionized state. In common usage, the words 'ionization energy' effectively refer to a given condition of the subject, used as a qualifier for the information regarding the ionized material or source of energy.
Examples of Ionization Energy:
It requires a certain amount of ionization energy to ionize iron.|
The amount of ionization energy must have been enormous, to ionize an entire planet.
The type of ionization energy involved must have been X rays, because there are no sources of other types of radiation.
Periodic trend for ionization energy. Each period begins at a minimum for the alkali metals, and ends at a maximum for the noble gases.