Hello Raju, Greetings!

According to Bohr's atomic theory, the energy of an electron in the stationary states around a nucleus of charge Ze is defined by quantum number n, and is given by, E (n) = - ( 2 π² m e⁴ Z²/n² h² ) in esu.

For hydrogen Z =1, and E( n ) = - ( 2 π² m e⁴/n² h² ).

The ionization energy is the energy to remove the electron from the bound state. In the present case the electron is in an excited state. So depending on the excited state the electron is in, the ionization energy will be 3.4ev or less.

Thank you.