From a hydrogen discharge tube, only three photons are picked up. The energies of these three photon — Atomic Structure Chemistry Question

💡 Solution & Explanation

The energies correspond to $n=2 \to 1$ (10.2 eV), $n=3 \to 1$ (12.1 eV), and $n=3 \to 2$ (1.9 eV). A single atom can emit the 1.9 eV and 10.2 eV photons in sequence, but emitting the 12.1 eV photon requires a separate atom that undergoes a direct $n=3 \to 1$ transition. Thus, at least two atoms are required. Therefore, correct answer is D.