1.3.3
Absorption & Emission Spectra
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Electromagnetic Radiation
Electromagnetic radiation is a continuous spectrum of waves with different energies.

The electromagnetic spectrum
- As the energy of waves changes across the electromagnetic spectrum so do both the frequency (𝜈) and wavelength (λ).
- Visible light makes up a small part of this spectrum.

Frequency and wavelength
- The frequency (𝜈) and wavelength (λ).of a wave are related by the following formula:
- c = 𝜈λ
- c is the speed of light.

Wave energy
- Frequency (𝜈) is multiplied by Planck’s constant (h) to give the energy (E) of the wave:
- E = h𝜈
- h = 6.63 × 10−34 Js
Absorption Spectra
Each element has a characteristic absorption spectrum depending on its electronic configuration.

Electron excitation
- When electromagnetic radiation is passed through a sample of gaseous atoms, specific energies of radiation are absorbed and cause electrons to be promoted (excited) to higher energy levels.

Absorption spectrum
- This produces an absorption spectrum and the frequencies of radiation that correspond to the energy gap for electrons to be excited are missing from the continuous spectrum.

Absorption spectra are unique
- The energy of an absorbed photon is the same as the energy gap for the electron excitation and this can be calculated from its frequency by using the following formula:
- ΔEelectron = h𝜈
- Each element has its own characteristic absorption spectrum as each element has a unique electron configuration.
Emission Spectra
Each element has a characteristic emission spectrum depending on its electron configuration.

Emission spectra
- After excitation, electrons can then relax back to lower energy levels to produce an emission spectrum.
- The emission lines occur at the same frequencies as the absorption lines in the absorption spectrum as the energy gaps for electrons to move are the same.

Balmer series
- Electrons that fall back to n = 2 correspond to transitions that release visible light and make up the Balmer series.

Significance
- The line emission spectrum gives us evidence for the Bohr model of an atom.
- The emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels.
- At high energy, lines start to become closer together and are said to converge. Energy levels converge at n = ∞ and when an electron reaches this level the atom has been ionised.
1Structure - Models of the Particulate of Matter
1.1Introduction to the Particulate Model of Matter
1.2The Nuclear Atom
1.3Electron Configuration
1.4Counting Particles by Mass: The Mole
1.6Elements, Compounds & Mixtures
1.7States of Matter & Changes of State
1.8Reacting Masses &. Volumes
1.9Solutions
2Structure - Models of Bonding & Structure
2.1The Ionic Model
2.2The Covalent Model
2.3Covalent Structures
2.4The Metallic Model
2.5From Models to Materials
2.6Valence Electrons & Ionic Compounds
2.7Molecular Shape
3Structure - Classification of Matter
3.1The Periodic Table: Classification of Elements
3.2Periodic Trends
3.3Group 1 Alkali Metals
3.4Halogens
3.5Noble gases, group 18
3.6Functional Groups: Classification of Organic
3.7Functional Group Chemistry
3.8Alkanes
3.9Alcohols
4Reactivity - What Drives Chemical Reaction?
4.1Endothermic & Exothermic Reactions
4.2Enthalpy of Reaction, Formation, & Hess' Law
5Reactivity - How Much, How Fast & How Far?
5.1Kinetics
5.2Rates of Reaction
5.3Stoichometry
5.4Le Châtelier’s Principle
5.5Introduction to Equilibrium
5.6Equilibrium Constant
5.7Reaction Quotient & Equilibrium Constant
6Reactivity - The Mechanisms of Chemical Change
6.1Proton Transfer Reactions
6.2The pH Scale
6.3Strong & Weak Acids and Bases
6.4Acid Deposition
6.5Types of Organic Reactions
6.6Oxidation & Reduction
6.7Electrochemical Cells
6.9Acid-Base Titrations
6.9.1Titration Calculation Weak Acid & Strong Base6.9.2Titration Experimental Detail6.9.3Extended Response - Titration6.9.4Titration Calculations6.9.5Titration Curves6.9.6Titration Calculation Strong Acid & Weak Base6.9.7IB Multiple Choice - Titrations6.9.8Polyprotic Acids6.9.9Titration Calculations Strong Acid & Strong Base6.9.10Titrations Curves 2
7Measurement, Data Processing & Analysis
7.1Uncertainties & Errors in Measurements & Results
7.2Graphical Techniques
7.3Spectroscopic Identification of Organic Compounds
7.4Infrared Spectroscpy
Jump to other topics
1Structure - Models of the Particulate of Matter
1.1Introduction to the Particulate Model of Matter
1.2The Nuclear Atom
1.3Electron Configuration
1.4Counting Particles by Mass: The Mole
1.6Elements, Compounds & Mixtures
1.7States of Matter & Changes of State
1.8Reacting Masses &. Volumes
1.9Solutions
2Structure - Models of Bonding & Structure
2.1The Ionic Model
2.2The Covalent Model
2.3Covalent Structures
2.4The Metallic Model
2.5From Models to Materials
2.6Valence Electrons & Ionic Compounds
2.7Molecular Shape
3Structure - Classification of Matter
3.1The Periodic Table: Classification of Elements
3.2Periodic Trends
3.3Group 1 Alkali Metals
3.4Halogens
3.5Noble gases, group 18
3.6Functional Groups: Classification of Organic
3.7Functional Group Chemistry
3.8Alkanes
3.9Alcohols
4Reactivity - What Drives Chemical Reaction?
4.1Endothermic & Exothermic Reactions
4.2Enthalpy of Reaction, Formation, & Hess' Law
5Reactivity - How Much, How Fast & How Far?
5.1Kinetics
5.2Rates of Reaction
5.3Stoichometry
5.4Le Châtelier’s Principle
5.5Introduction to Equilibrium
5.6Equilibrium Constant
5.7Reaction Quotient & Equilibrium Constant
6Reactivity - The Mechanisms of Chemical Change
6.1Proton Transfer Reactions
6.2The pH Scale
6.3Strong & Weak Acids and Bases
6.4Acid Deposition
6.5Types of Organic Reactions
6.6Oxidation & Reduction
6.7Electrochemical Cells
6.9Acid-Base Titrations
6.9.1Titration Calculation Weak Acid & Strong Base6.9.2Titration Experimental Detail6.9.3Extended Response - Titration6.9.4Titration Calculations6.9.5Titration Curves6.9.6Titration Calculation Strong Acid & Weak Base6.9.7IB Multiple Choice - Titrations6.9.8Polyprotic Acids6.9.9Titration Calculations Strong Acid & Strong Base6.9.10Titrations Curves 2
7Measurement, Data Processing & Analysis
7.1Uncertainties & Errors in Measurements & Results
7.2Graphical Techniques
7.3Spectroscopic Identification of Organic Compounds
7.4Infrared Spectroscpy
Practice questions on Absorption & Emission Spectra
Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.
- 1What is the symbol for wavelength?Multiple choice
- 2What is the correct equation for the energy of a wave?Multiple choice
- 3
- 4Which of these statements is correct?Multiple choice
- 5
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