5.1.4

Discrete Energy Levels

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Energy Levels in Atoms

Electrons in atoms must occupy a discrete energy level.

Energy levels

Energy levels

  • Electrons do not float around randomly in atoms.
  • They can only be found at set energy levels.
  • Each energy level is given a 'quantum number'.
  • The ground state is the lowest energy level. The ground state has n = 1.
  • The higher the energy level, the larger its quantum number, n.
Transitions between energy levels

Transitions between energy levels

  • An electron can transition between energy levels by absorbing or emitting a photon of a specific frequency.
  • If an electron emits a photon, it will drop in energy level.
  • If an electron absorbs a photon, it will rise to a higher level.
    • In both cases, the photon must have energy exactly equal to the energy difference between the levels.
Equation

Equation

  • The movement of electrons between energy levels can be represented in the equation:
    • ΔE=E1−E2=hf=hcλ\Delta E = E_1 - E_2 = hf = \frac{hc}{\lambda}
  • This shows that the energy difference between levels one and two is equal to the energy of the emitted (or absorbed) photon.
Excitation and ionization

Excitation and ionization

  • If an electron absorbs a photon and jumps up an energy level, we say it has been excited.
  • If an electron absorbs a photon that is so energetic it is knocked out of the atom altogether, the electron has been ionized.

Ionization and Excitation

Both electrons being removed from an atom and the movement of electrons within energy levels in the atom explain commonly observed phenomena.

Ionization

Ionization

  • To ionize an atom means to remove or add electrons to an atom.
  • Ionization in the context of quantum phenomena almost always means the removal of electrons completely from the atom.
  • The energy needed for an electron to go from the ground state to be completely removed is called the ionization energy.
Excitation

Excitation

  • Electrons can also be made to move from one energy level to the other.
  • To do this, the electron needs exactly the energy difference between energy levels.
  • One way to do this is for a photon to interact with the electron.
  • The electron will absorb all the energy of the photon.
Excitation 2

Excitation 2

  • If the energy of the photon is exactly the energy difference between the energy levels, the electron will move up the energy levels.
  • When an electron has moved up energy levels we called the electron "excited".
  • The process of making the electron move up energy levels is called "excitation".
Jump to other topics
1

Space, Time & Motion

1.1

Motion

1.1.1Motion Basics1.1.2Graphs of Motion1.1.3Uniform Acceleration Equations1.1.4Projectile Motion1.1.5Bouncing Ball Example
1.2

Forces

1.2.1Friction1.2.2Terminal Speed1.2.3Newton's Laws1.2.4Exam-Style Question - Forces1.2.5End of Topic Test - Newton's Third Law
1.3

Momentum & Impulse

1.3.1Momentum1.3.2Momentum 21.3.3End of Topic Test - Newton's Laws & Momentum
1.4

Work, Energy & Power

1.4.1Work & Energy1.4.2Conservation of Energy1.4.3Power & Efficiency1.4.4IB Multiple Choice- Work, Energy & Power
2

The Particulate Nature of Matter

2.1

Thermal Concepts

2.1.1Molecular Kinetic Theory Model2.1.2Molecular Kinetic Theory Model 22.1.3Thermal Energy Transfer2.1.4Thermal Energy Transfer Experiments2.1.5Thermal Equilibrium2.1.6Thermal Conductivity2.1.7Heat Energy Transfer
2.2

Modelling a Gas

2.2.1Ideal Gases2.2.2Ideal Gases 22.2.3End of Topic Test - Thermal Energy & Ideal Gases2.2.4Exam-Style Question - Ideal Gases
3

Wave Behaviour

3.1

Oscillations

3.1.1Progressive Waves3.1.2Simple Harmonic Motion
3.2

Travelling Waves

3.2.1Wave Speed & Phase Difference3.2.2Longitudinal & Transverse Waves3.2.3Electromagnetic Waves3.2.4Electromagnetic Waves 23.2.5Sound Waves
3.3

Wave Characteristics

3.3.1Polarisation
3.4

Wave Behaviour

3.4.1Reflection & Absorption3.4.2Reflection of Light3.4.3Refraction3.4.4Refractive index
3.5

Standing Waves

3.5.1Standing Waves3.5.2Standing Waves 23.5.3End of Topic Test - Standing Waves3.5.4IB Multiple Choice - Waves
3.6

Simple Harmonic Motion

3.6.1Simple Harmonic Motion3.6.2Simple Harmonic Systems3.6.3Energy in Simple Harmonic Motion3.6.4End of Topic Test - Simple Harmonic Motion3.6.5End of Topic Test - Simple Harmonic Motion
3.7

Single Slit Diffraction

3.7.1Diffraction
3.8

Interference

3.8.1Interference3.8.2Interference 23.8.3Diffraction Gratings3.8.4End of Topic Test - Diffraction
3.9

Doppler Effect

3.9.1Doppler Effect
4

Fields

4.1

Circular Motion

4.1.1Circular Motion4.1.2Centripetal Force4.1.3IB Multiple Choice - Circular Motion
4.2

Newton's Law of Gravitation

4.2.1Newton's Law4.2.2Orbits of Planets & Satellites4.2.3Escape Velocity & Synchronous Orbits4.2.4End of Topic Test - Gravitational Fields
4.3

Fields

4.3.1Fields4.3.2Gravitational Field Strength4.3.3Gravitational Potential4.3.4Electric Field Strength4.3.5Electrostatic & Gravitational Forces4.3.6Electric Potential4.3.7IB Multiple Choice - Gravitational Fields
4.4

Fields at Work

4.4.1Radial Field Strength4.4.2Orbits of Planets & Satellites4.4.3Escape Velocity & Synchronous Orbits4.4.4End of Topic Test - Gravitational Fields4.4.5Uniform Electric Fields4.4.6IB Multiple Choice - Electric Field & Potential
4.5

Electric Fields

4.5.1Electric Charge4.5.2Conservation of Charge4.5.3Coulomb's Law4.5.4Current4.5.5Potential Difference4.5.6IB Multiple Choice - Electric Charge
4.6

Magnetic Effect of Electric Currents

4.6.1Magnetism4.6.2Magnetic Field4.6.3Magnetic Force4.6.4Moving Charges in a Magnetic Field4.6.5IB Multiple Choice - Magnetism
4.7

Heating Effect of Currents

4.7.1Circuits4.7.2Resistance4.7.3Power and Conservation4.7.4IB Multiple Choice - DC Circuits
4.8

Electromagnetic Induction

4.8.1Electromagnetic Induction4.8.2Electromagnetic Induction 24.8.3Magnetic Flux & Flux Linkage4.8.4End of Topic Test - Electromagnetic Induction
4.9

Power Generation & Transmission

4.9.1Alternating Currents4.9.2Operation of a Transformer
4.10

Capacitance

4.10.1Capacitance4.10.2Parallel Plate Capacitor4.10.3Energy Stored by a Capacitor4.10.4Capacitor Discharge4.10.5Capacitor Charge4.10.6Magnetic Flux Density4.10.7End of Topic Test - Capacitance & Flux Density
5

Nuclear & Quantum Physics

5.1

Discrete Energy & Radioactivity

5.1.1Atomic Spectra5.1.2Atomic Structure5.1.3Photons5.1.4Discrete Energy Levels5.1.5Alpha, Beta & Gamma Radiation5.1.6Scientific Practices - Unstable Nuclei5.1.7Radioactive Decay5.1.8IB Multiple Choice - Atomic Physics
5.2

Nuclear Reactions

5.2.1Mass & Energy5.2.2Nuclear Fission
5.3

The Interaction of Matter with Radiation

5.3.1Particles, Antiparticles & Photons5.3.2Particle Interactions5.3.3Classification of Particles5.3.4Wave-Particle Duality5.3.5Wave Functions & Probability5.3.6IB Multiple Choice - Quantum Physics
5.4

Nuclear Physics

5.4.1Nuclear Instability & Radioactive Decay5.4.2Nuclear Radius5.4.3IB Multiple Choice - Nuclear Physics
6

Measurements

6.1

Measurements & Errors

6.1.1Fundamental Units6.1.2SI Prefixes, Standard Form & Converting Units6.1.3End of Topic Test - Units & Prefixes
6.2

Uncertainties & Errors

6.2.1Limitation of Physical Measurements6.2.2Uncertainty6.2.3Estimation6.2.4End of Topic Test - Measurements & Errors
6.3

Vectors & Scalars

6.3.1Scalars & Vectors6.3.2Vector Problems

Practice questions on Discrete Energy Levels

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    What is the quantum number for the ground state of an electron?Multiple choice
  2. 2
    What is the correct equation for the change in energy between energy levels?Multiple choice
  3. 3
    In the field of quantum physics, ionization almost always means that electrons have been:Multiple choice
  4. 4
    When will an electron move into a higher energy level?Multiple choice
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Photons

Alpha, Beta & Gamma Radiation