Excitation and Ionization Potential

Excitation Potential

• The energy required to raise an atom from its ground state to an excited state is called the excitation energy.
• Under normal conditions, hydrogen atoms are usually in their lowest energy state where n = 1. This is called ground state of hydrogen atoms. However, if the atoms are exposed to incident energy from outside, they absorb energy and shift to a higher energy state.

Let us suppose we have to take the electron of hydrogen atom from first to second orbit.

We know,

Energy of electron in first orbit = -13.6 eV

Energy of electron in second orbit = -3.4 eV

∴ The required amount of energy to take a hydrogen atom from first to second orbit

= (-3.4 eV) – (-13.6 eV)

= 10.2 eV

Similarly, in order to excite an atom from first to third orbit is calculated as follows.

Energy of the first orbit = -13.6 eV

Energy of the third orbit = – 1.51 eV

Required amount of energy = (-1.51 eV) – (-13.6 eV)

= 12.09 eV

If an atom is raised to an excited state from its ground state by applying energy eV then, V is called excitation potential of the atom.

Thus, if the excitation energy is 10.2 eV for hydrogen atom from first to second orbit then 10.2 eV is the excitation potential for it. In other words, this energy 10.2 eV can be acquired by the electron if it is accelerated between two electrodes having a potential difference 10.2 eV.

Similarly, the excitation potential of hydrogen atom for an electron which jumps from the first to third orbit is 12.09 V. Thus, the excitation potential of an energy of an atom can be defined as the potential, which is required for an electron to jump from the ground state to any one of its excited states.

Ionization Potential

The minimum amount of energy required to remove an electron completely from an atom is called ionization energy. When an electron is removed from the atom, the atom is said to be ionized.

Let us calculate the ionization energy of a hydrogen atom, when the electron is in the first orbit.

Energy of electron in the first orbit = 13.6 eV

Energy of electron in the outer most orbit (n = ∞) = 0

∴ Required amount of energy = 0 – (-13.6) eV

Hence, ionization energy = 13.6 eV

This shows that to remove the electron completely from the orbit to infinity, the potential difference of 13.6 V must be applied. This is called ionization potential.

Thus, ionization potential is defined as the minimum potential to be applied in order to remove the electron completely from its ground state to infinity.

References: 

i) https://www.differencebetween.com/difference-between-excitation-and-vs-ionization-potential/

ii) https://www.brainkart.com/article/Excitation-and-ionization-potential-of-an-atom_2925/

iii) https://qsstudy.com/excitation-and-ionization-potential-of-an-atom/

Excitation and Ionization Potential