Ionization energy

Ionization energy is the energy needed to remove electron from an atom in gaseous state. An atom is neutral in charge. If an atom required to transform into positive ion there need one or more electron remove. We know each of the electron orbits surrounding the nucleus with maintaining an attraction force between nucleus and atom. To remove an electron from an atomic shell there needs to overcome the attraction force between nucleus and electron.  This energy is termed as ionization energy. Unit of ionization energy is eV per atom or kilojoules per mole. One eV is equal to 96.84 kilojoul per mole. Ionization energy is also called ionization potential. Ionization energy may classified into different class. Such as first ionization energy and second ionization energy. First ionization is the required energy in order to remove first electron from the atom. After removing one electron from atom, if there required another electron to remove from atom there need additional amount of energy to remove the second electron. This required energy is called second ionization energy. For sufficient of ionization energy the electron removes from the neutral atom and finally atom is convert into ion.