Log In
Log In
Led by Ernest Rutherford Simulacrum
Six tutorials covering AQA GCSE Physics §4.4 Atomic Structure — the structure of the atom, the historical development of the atomic model, radioactive decay, half-lives, hazards and uses of radiation, and nuclear fission and fusion — taught by simulacra of the physicists who opened the atom up and mapped what they found inside.
Courses are available to holders of a paid pass or membership. See passes & membership →
Led by Niels Bohr Simulacrum
The question
What is an atom made of, how big is it, and what makes two atoms of the same element different?
Territory
atom radius approximately 1 × 10⁻¹⁰ m · nucleus composed of protons and neutrons · radius of nucleus less than 1/10,000 radius of atom · most of atomic mass in nucleus · electrons at different energy levels (different distances from nucleus) · electron transitions by absorption and emission of electromagnetic radiation · atomic number = number of protons · mass number = total protons and neutrons · number of electrons equals number of protons (neutral atom) · isotopes: same element, different neutron count · positive ions formed when outer electrons are lost · standard notation for atoms
Outcome
The student can describe the structure of the atom with correct relative sizes, explain electron energy levels and transitions, define atomic number, mass number, isotopes, and ions, and read the standard notation for a specified nuclide. (AQA 4.4.1.1, 4.4.1.2)
Led by Ernest Rutherford Simulacrum
The question
How does a scientific model change? Walk through the evidence that took us from "indivisible sphere" to "nucleus-with-electrons" in less than fifty years.
Territory
before the electron: atoms thought to be indivisible spheres · Thomson's plum pudding model (ball of positive charge with embedded negative electrons) · Rutherford's alpha particle scattering experiment · what the experiment showed: mass concentrated at a small charged centre · the nuclear model replaces the plum pudding model · Bohr adapts the nuclear model with orbital energy levels · Bohr's theoretical calculations agree with observation · the proton: positive charge of the nucleus subdivided into identical units · Chadwick's neutron (about twenty years after the nucleus became accepted) · why new evidence forces model change · what scientific models are for · (details of Bohr's experimental support and of Chadwick's experiment are NOT required)
Outcome
The student can describe the sequence from indivisible sphere to plum pudding to nuclear model to Bohr model to neutron, explain why the alpha scattering experiment forced the change from plum pudding to nuclear, and articulate the principle that scientific models are provisional and change when new evidence arrives. (AQA 4.4.1.3)
Led by Marie Curie Simulacrum
The question
Some atomic nuclei spontaneously emit radiation. What are they emitting, and why?
Territory
some atomic nuclei are unstable and emit radiation to become more stable · radioactive decay is a random process · activity in becquerel (Bq) · count-rate recorded by detectors such as the Geiger-Müller tube · alpha particle (α) = 2 protons + 2 neutrons = helium nucleus · beta particle (β) = high-speed electron ejected from nucleus as a neutron becomes a proton · gamma ray (γ) = electromagnetic radiation from the nucleus · neutron emission · properties: penetrating power through materials, range in air, ionising power · nuclear equations for alpha and beta decay (balancing mass numbers and atomic numbers — identification of daughter elements is NOT required) · gamma emission changes neither mass nor charge
Outcome
The student can name the four types of nuclear radiation, describe each in terms of composition, penetration, range, and ionisation, explain the difference between activity and count-rate, and write balanced nuclear equations for single alpha and beta decays. (AQA 4.4.2.1, 4.4.2.2)
Led by Lise Meitner Simulacrum
The question
If radioactive decay is a random process, how can it have a predictable half-life?
Territory
radioactive decay is random · half-life = time for the number of undecayed nuclei (or count-rate, or activity) to halve · determining half-life from experimental data or graphs · (Higher Tier) calculating the net decline as a ratio after a given number of half-lives · contamination (unwanted presence of radioactive material on or in another material) vs irradiation (exposure to radiation — the irradiated object does NOT become radioactive) · precautions for both · the importance of peer review in validating findings about the biological effects of radiation
Outcome
The student can define half-life, determine it from a graph or table, (Higher Tier) calculate net decline as a ratio after a given number of half-lives, explain the difference between contamination and irradiation, and discuss why findings on radiation's biological effects must be peer-reviewed. (AQA 4.4.2.3, 4.4.2.4)
Led by Richard Feynman Simulacrum
The question
Radiation is genuinely dangerous and also genuinely useful. How do we think clearly about when to use it, what to protect against, and what "background" radiation actually is?
Territory
background radiation from natural sources (rocks, cosmic rays) and man-made sources (weapons testing fallout, accidents, medical) · radiation dose in sieverts and millisieverts (recalling the unit is NOT required) · how occupation and location affect dose · different half-lives give different hazard profiles · uses of nuclear radiation in medicine: exploration of internal organs (imaging with short-half-life tracers), control or destruction of unwanted tissue · evaluating the perceived risks in relation to quantitative data · the distinction between the scientific question (what is the risk?) and the human question (is it worth it?)
Outcome
The student can identify natural and man-made sources of background radiation, explain how occupation and location affect dose, reason about how half-life affects hazard, describe and evaluate the use of nuclear radiation in imaging and treatment, and weigh quantitative risk information against benefit. (AQA 4.4.3.1, 4.4.3.2, 4.4.3.3)
Led by Enrico Fermi Simulacrum
The question
You can get enormous amounts of energy either by splitting heavy nuclei apart or by forcing light nuclei together. How do these two processes work, and what is the same about them?
Territory
nuclear fission: splitting of a large and unstable nucleus (e.g. uranium, plutonium) · spontaneous fission is rare · fission usually requires the nucleus to absorb a neutron first · products: two smaller nuclei roughly equal in size, two or three neutrons, gamma rays · energy is released; fission products carry kinetic energy · chain reaction arises when emitted neutrons trigger further fission · controlled chain reaction in a nuclear reactor · uncontrolled chain reaction in a nuclear weapon · drawing and interpreting diagrams of fission and chain reactions · nuclear fusion: joining of two light nuclei into a heavier one · in fusion some of the mass may be converted into the energy of radiation · the sun as a fusion reactor
Outcome
The student can describe nuclear fission in full (with neutrons, products, energy release, and chain reaction), describe nuclear fusion, draw and interpret diagrams of a fission chain reaction, and articulate the difference between controlled (reactor) and uncontrolled (weapon) chain reactions. (AQA 4.4.4.1, 4.4.4.2)