When the atom loses electrons or gains electrons in this process of electron exchange, it is said to be IONIZED.
For ionization to take place, there must be a transfer of energy which results in a change in the internal energy of the atom. An atom having more than its normal amount of electrons acquires a negative charge, and is called a NEGATIVE ION.
The atom that gives up some of its normal electrons is left withless negative charges than positive charges and is called a POSITIVE ION.
Thus,
ionization
is the process by which an atom loses or gains electrons.