Lesson Plan

• Describe the quantisation of electron energy levels in isolated atoms.
• Explain how electron transitions produce line spectra using the Bohr model and the Rydberg formula.
• Calculate wavelengths of hydrogen spectral lines for given transitions.
• Interpret the Lyman, Balmer, and Paschen series and relate them to specific energy‑level changes.
• Identify common misconceptions about atomic electron behaviour.

• Projector or interactive whiteboard
• Slides with energy‑level diagrams and spectra
• Handouts of the Rydberg formula and sample calculations
• Spectroscopy simulation software or online app
• Scientific calculators
• Worksheet for practice problems

Begin with a striking image of a hydrogen emission spectrum and ask students what determines the distinct coloured lines. Recall prior learning about photons and energy conservation, linking it to electron transitions in atoms. Explain that by the end of the lesson they will be able to predict line wavelengths and explain why the spectrum is discrete.

1. Do‑now (5'): Quick quiz on photon energy (E = hν) to activate prior knowledge.
2. Mini‑lecture (10'): Present the Bohr model, quantised orbits, and derive the allowed energy levels.
3. Guided derivation (10'): Work through the Rydberg formula on the board; students fill in missing steps.
4. Interactive simulation (10'): Students explore hydrogen spectral series using spectroscopy software and record observed wavelengths.
5. Practice problem (10'): Calculate the Balmer‑α wavelength using the Rydberg formula; peer‑check answers.
6. Check for understanding (5'): Exit ticket – one sentence explaining why line spectra prove discrete energy levels.

Summarise that discrete electron energy levels cause the observed line spectra and that the Bohr model and Rydberg formula accurately predict them. Have students write an exit ticket stating one real‑world application of spectral lines. Assign homework: complete a worksheet extending calculations to the Paschen series.