7. Atomic, nuclear and particle physics
7. Atomic, nuclear and particle physics
7.1 – Discrete energy and radioactivity
Nature of science:
Accidental discovery: Radioactivity was discovered by accident when Becquerel developed photographic film that had accidentally been exposed to radiation from radioactive rocks. The marks on the photographic film seen by Becquerel probably would not lead to anything further for most people. What Becquerel did was to correlate the presence of the marks with the presence of the radioactive rocks and investigate the situation further.
Understandings:
Discrete energy and discrete energy levels
Transitions between energy levels
Radioactive decay
Fundamental forces and their properties
Alpha particles, beta particles and gamma rays
Half-life
Absorption characteristics of decay particles
Isotopes
Background radiation
Applications and skills:
Describing the emission and absorption spectrum of common gases
Solving problems involving atomic spectra, including calculating the wavelength of photons emitted during atomic transitions
Completing decay equations for alpha and beta decay
Determining the half-life of a nuclide from a decay curve
Investigating half-life experimentally (or by simulation)
7.2 – Nuclear reactions
Nature of science:
Patterns, trends and discrepancies: Graphs of binding energy per nucleon and of neutron number versus proton number reveal unmistakable patterns. This allows scientists to make predictions of isotope characteristics based on these graphs.
Understandings:
The unified atomic mass unit
Mass defect and nuclear binding energy
Nuclear fission and nuclear fusion
Applications and skills:
Solving problems involving mass defect and binding energy
Solving problems involving the energy released in radioactive decay, nuclear fission and nuclear fusion
Sketching and interpreting the general shape of the curve of average binding energy per nucleon against nucleon number
7.3 – The structure of matter
Nature of science:
Predictions: Our present understanding of matter is called the Standard Model, consisting of six quarks and six leptons. Quarks were postulated on a completely mathematical basis in order to explain patterns in properties of particles. Collaboration: It was much later that large-scale collaborative experimentation led to the discovery of the predicted fundamental particles.
Understandings:
Quarks, leptons and their antiparticles
Hadrons, baryons and mesons
The conservation laws of charge, baryon number, lepton number and strangeness
The nature and range of the strong nuclear force, weak nuclear force and electromagnetic force
Exchange particles
Feynman diagrams
Confinement
The Higgs boson
Applications and skills:
Describing the Rutherford-Geiger-Marsden experiment that led to the discovery of the nucleus
Applying conservation laws in particle reactions
Describing protons and neutrons in terms of quarks
Comparing the interaction strengths of the fundamental forces, including gravity
Describing the mediation of the fundamental forces through exchange particles
Sketching and interpreting simple Feynman diagrams
Describing why free quarks are not observed
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