Question

The term ionization energy refers to the minimum amount of energy we need to supply to remove an electron completely from the atom. Consider the ground state of the hydrogen atom. The ionization energy would be ________ eV.
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Answer 1

It is given that the atom is in its ground state - the electron must be in the orbit n=1, bound to the proton by an energy of -13.6 eV. This basically means, if I somehow supply 13.6 eV to the electron, or higher, the electron will come out of the atom, leaving an ionized atom behind. The ionization energy, in this case, must be 13.6 eV then.