The ionization energy IE or free ionization enthalpy (also: ionisation energy, ionization potential) describes the energy required to remove an electron from a neutral or a partially ionized, gaseous atom or molecule (ionization):

A + IE → A⁺ + e^-.

The energy for the separation of the first electron is called 1st ionization energy, that for the second electron is called 2nd ionization energy and that for the nth electron is called nth ionization energy.

Ionization energies are given in eV for single electrons or in kJ/mol for 1 mole = NA (Avogadro's constant) electrons (molar ionization energy); the conversion factor is:

1 electronvolt eV = 96.485307 kJ mol^-1.

Ionization energies 1 to 5

Table with the first (IE1) to fifth (IE5) ionization energies of the chemical elements in eV.

Ionization energies 5 to 9

Table with the sixth (IE6) to ninth (IE9) ionization energies of the elements in eV.

References:

[1] - Jean Sansonetti: NIST Ground Levels and Ionization Energies for the Neutral Atoms.

[2] - J. E. Sansonetti, W. C. Martin, S. L. Young: NIST Handbook of Basic Atomic Spectroscopic Data.

[3] - Darleane C. Hoffman, Diana M. Lee, Valeria Pershina:
Transactinide Elements and Future Elements.
In: The Chemistry of the Actinide and Transactinide Elements, Springer, (2006), ISBN 1402035551.

Last update: 2024-08-26

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