# Explain why the line emission spectrum of hydrogen consists of series of discrete lines at specific frequencies, and why these lines are grouped into distinct series such as the Lyman and Balmer series.

> IB DP Chemistry Higher Level (2023 syllabus) — S1.2 The nuclear atom · Explain · 4 marks

## Mark scheme (4 marks)

1. Electrons in a hydrogen atom exist only in specific, quantised energy levels (shells/orbitals), not in a continuum of energies.
2. When an electron falls from a higher energy level to a lower energy level, it emits a photon of electromagnetic radiation whose frequency (or energy) corresponds exactly to the difference in energy between those two levels.
3. Because only specific energy level differences are possible, only specific frequencies of light are emitted, producing discrete lines rather than a continuous spectrum.
4. Each series corresponds to all electron transitions that end (terminate) at the same lower energy level; the Lyman series involves transitions to n = 1 (ultraviolet region) and the Balmer series involves transitions to n = 2 (visible region), so different series appear in different regions of the electromagnetic spectrum.

## Key terms

- [line emission spectrum](https://www.gradenine.co.uk/glossary/line-emission-spectrum)
- [Balmer series](https://www.gradenine.co.uk/glossary/balmer-series)

## Related

- [Revision notes for IB DP Chemistry Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-line-emission-spectrum-2589a57b) · Published by Druglandscape Ltd.