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1.3.2—Hydrogen emission spectrum

Syllabus
First assessment 2025
Objective
1.3.2
Level
SL

Hydrogen's Line Spectrum

Hydrogen's emission spectrum contains discrete lines because electrons occupy discrete energy levels. Each line corresponds to a downward transition and the emitted photon's energy equals the energy difference between the levels.

Hydrogen transitions end at n equals 1, 2, or 3, and the resulting spectral lines crowd together toward the high-energy convergence limit.
Hydrogen transitions end at n equals 1, 2, or 3, and the resulting spectral lines crowd together toward the high-energy convergence limit.
Transition ending at Region identified in the study guide
n = 1 ultraviolet
n = 2 visible
n = 3 infrared

At higher energy, the levels become closer together, so the lines converge. The names of the series are not required.

Use the presence of separate lines as evidence for discrete levels, and use convergence at higher energy or frequency as evidence that the level spacing becomes smaller.

Compare lines by their energy gaps. Transitions ending at n = 2 form the visible series, and lines crowd together as the starting level rises because adjacent high-n levels are closer in energy. The convergence limit represents removal of the electron, not one more bound-state transition.

Interpreting Hydrogen Emission Lines

[ 3 ]

Explain how this spectrum is related to the electron energy levels in a hydrogen atom.

Electron Configurations Summary

Retrieve the chain: emission lines reveal discrete levels; capacities, sublevels, orbitals, and spin rules build configurations; first and successive ionization energies then reveal how electrons are held and arranged.

When checking an answer, ask: Did I link a line to a transition? Did I use 2n² and the filling rules? Did I explain an ionization trend or count electrons before a successive-IE jump?