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A hydrogen atom in its ground state absorbs a photon of energy 12.09 eV. To which principal quantum number does the electron move?

Answer: n = 3.

A n = 2
B n = 3
C n = 4
D n = 5

Correct answer: B. n = 3

Explanation: The energy required for the transition from n = 1 to n = 3 is 13.6(1 - 1/9) = 12.09 eV. Hence the electron moves to n = 3.

Comparison of the Thomson model and the Rutherford model of the atom: in the Thomson plum pudding model alpha particles pass almost straight through a diffuse positive sphere, while in the Rutherford model a concentrated central nucleus deflects some alpha particles through large angles, with the lower panels showing the alpha particle source and gold foil and the observed result of wide-angle scattering

The Geiger–Marsden alpha-scattering result: a few alpha particles bounce back at large angles, which rules out Thomson’s diffuse model and demands a tiny, massive, positively charged nucleus. Image: Kurzon, CC BY 3.0, via Wikimedia Commons.

Concept context

Thomson's plum-pudding model, Rutherford's nuclear model from alpha-scattering, Bohr's postulates and hydrogen spectrum, spectral series (Lyman to Pfund), Rydberg formula, and limitations of each model.

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A hydrogen atom in its ground state absorbs a photon of energy 12.09 eV. To which principal quantum number does the electron move?

Concept context

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