A hydrogen atom is already in its third Bohr orbit. What is the minimum additional energy required to ionise the atom from this excited state?
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Question

A hydrogen atom is already in its third Bohr orbit. What is the minimum additional energy required to ionise the atom from this excited state?

G1 Physics · Accepted Answer

The third-orbit energy is E₃ = −13.6 ÷ 9 ≈ −1.511 eV. To ionise the atom, the electron must be raised to the continuum level E = 0. Required energy: E(ion from n=3) = 0−E₃ = 1.511 eV. Thus the minimum required energy is approximately 1.51 eV. Correct option: B.