Hydrogen Spectrum: Emission and Absorption

Hydrogen Spectrum: Emission and Absorption

Year 13 Chemistry/Physics Understanding Atomic Line Spectra 50-minute lesson

WALT (We Are Learning To)

Explain the hydrogen emission spectrum and its characteristic lines Describe the difference between emission and absorption spectra Identify and analyze the Balmer, Lyman, and Paschen series Apply Bohr's model to explain spectral lines Calculate wavelengths and frequencies of spectral transitions

Success Criteria

I can identify the main series in hydrogen spectrum I can explain why hydrogen produces line spectra rather than continuous spectra I can calculate energy differences between electron levels I can distinguish between emission and absorption processes I can apply the Rydberg equation to solve problems

What happens when you heat hydrogen gas?

Think about what you observe when elements are heated Consider what this tells us about atomic structure

What is a Spectrum?

A spectrum shows how light is distributed across different wavelengths Continuous spectrum: all wavelengths present (like a rainbow) Line spectrum: only specific wavelengths present Each element has a unique 'fingerprint' spectrum

Emission vs Absorption Spectra

{"left":"Emission Spectrum: Bright lines on dark background\nProduced when excited atoms release energy\nElectrons fall from higher to lower energy levels\nEnergy is emitted as photons of specific wavelengths","right":"Absorption Spectrum: Dark lines on bright background\nProduced when atoms absorb specific wavelengths\nElectrons jump from lower to higher energy levels\nMissing wavelengths appear as dark lines"}

The Hydrogen Atom Model

Simplest atom: one proton, one electron Electron exists in specific energy levels (not orbits) Energy levels are quantized (fixed values) Ground state: lowest energy level (n=1) Excited states: higher energy levels (n=2, 3, 4...)

Energy Level Transitions

Draw hydrogen energy levels from n=1 to n=6 Mark possible electron transitions with arrows Identify which transitions produce visible light Calculate energy differences using E = -13.6/n² eV

The Balmer Series

Transitions ending at n=2 energy level Produces visible light (400-700 nm) Four main lines: Hα, Hβ, Hγ, Hδ Red line (656 nm): n=3→n=2 transition Blue-green line (486 nm): n=4→n=2 transition

Hydrogen Spectral Series Overview

The Lyman Series (UV)

Transitions ending at n=1 (ground state) Produces ultraviolet radiation Highest energy transitions Important in stellar astronomy Lyman-alpha line: n=2→n=1 (121.6 nm)

The Paschen Series (Infrared)

Transitions ending at n=3 energy level Produces infrared radiation Lower energy than visible light Detected using special IR equipment Important in atmospheric studies