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.
| 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
Assessment in practice
2–3 marks in the two selected direct examples marksHow it is assessed
Structured questions ask learners to describe hydrogen's discrete line spectrum and explain how each line corresponds to an electron energy difference and how the lines converge at higher energy.
Command terms
describe / explain
What earns marks
Identify discrete lines or specific wavelengths/frequencies, connect each line to a downward transition and its energy difference, and state that energy levels become closer together at higher energy, producing convergence.
Watch for
Calling the hydrogen spectrum continuous, reversing the downward emission transition, or placing convergence at lower rather than higher energy or frequency.
Representative question
Question 1
[Maximum number: 3]
Explain how this spectrum is related to the electron energy levels in a hydrogen atom.
each transition/line is related to energy difference /ΔE=λhf/hv/hc;
energy levels in hydrogen atom are closer/converge at higher energy;
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?