A proton and an electron, both at rest initially, combine to form a hydrogen atom in the ground stat — Atomic Structure Chemistry Question

💡 Solution & Explanation

The formation of a hydrogen atom in its ground state from a free electron and proton corresponds to the electron transitioning from $n = \infty$ to $n = 1$. The energy emitted is the ionization energy of hydrogen, which is 13.6 eV. The wavelength of the emitted photon is $\lambda = \frac{1240 \text{ eV}\cdot\text{nm}}{13.6 \text{ eV}} \approx 91.17$ nm. Rounding to the nearest integer gives 91 nm. Therefore, correct answer is 0091.