What is the minimum energy required to ionize

a hydrogen atom in the n = 3 state?

(1) 0.00 eV (3) 1.51 eV

(2) 0.66 eV (4) 12.09 eV

(3) 1.51 eV The binding energy of an electron in the n = 3 state is E = - Eo/n^2 where Eo = 13.6 eV. So E3 = - 13.6eV/9 = - 1.51eV. The minimum energy required to overcome this binding energy is 1.51eV