The ionization energy of hydrogen atom in the ground state is

The ionization energy of hydrogen atom in the ground state is

13.6 MeV
13.6 eV
13.6 Joule
Zero
This question was previously asked in
UPSC NDA-2 – 2017
The ionization energy of a hydrogen atom is the minimum energy required to remove the electron from the ground state (n=1) and take it to the ionization limit (n=infinity).
The energy of an electron in the n-th energy level of a hydrogen atom is given by E_n = -13.6/n² eV. In the ground state (n=1), the energy is E₁ = -13.6/1² = -13.6 eV. At the ionization limit (n=infinity), the energy is E_infinity = -13.6/infinity² = 0 eV. The ionization energy is the difference between these energies: Ionization Energy = E_infinity – E₁ = 0 – (-13.6 eV) = +13.6 eV.
MeV (Mega electron Volt) and Joule are also units of energy, but 13.6 eV is the standard and correct value for the hydrogen atom’s ionization energy. 1 eV is approximately 1.602 x 10⁻¹⁹ J. 1 MeV is 10⁶ eV. 13.6 MeV is an extremely large amount of energy in this context. Zero ionization energy would mean no energy is required to remove the electron, which is incorrect for a bound electron.