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33 exam-style questions with model answers, plus 44 quick multi-choice questions — every question on the site for this standard, grouped by the 11 pages of notes they come from.
Write a full answer before you reveal the model one — that comparison is where the marks come from. Every block links back to the notes that teach it.
Describe Thomson's 'plum pudding' model of the atom.
Explain why Thomson's model predicted that alpha particles fired at a thin gold foil would pass through with only very small deflections.
Discuss how the change from Thomson's model to Rutherford's model shows the way scientific models are developed and replaced, linking this to the evidence available at each stage.
In the gold foil experiment, state what happened to the majority of the alpha particles, and what this shows about the structure of the atom.
Explain why a very thin gold foil, and a vacuum, were both necessary for the experiment to give a clear result.
Using the results of the gold foil experiment, explain fully how the size, charge and mass of the nucleus can each be deduced, and link these deductions to why the alpha particle is a suitable probe for this experiment.
An atom is represented as .
State the number of protons and the number of neutrons in this atom.
Two atoms are represented as and .
Explain what these two atoms are to each other, and state one way in which they are the same and one way in which they differ.
A small nucleus tends to be stable with roughly equal numbers of protons and neutrons, but a large nucleus needs proportionally more neutrons than protons to be stable.
Explain fully why this is the case, referring to the forces acting inside the nucleus.
State what an alpha particle is made of, and state its relative charge.
A student places a Geiger counter next to a radioactive source. The count rate drops sharply when a single sheet of paper is placed in the way, but a further increase in shielding to several mm of aluminium makes almost no additional difference.
Explain what this tells you about the type(s) of radiation being emitted.
A radioactive source emitting all three types of radiation is placed between two charged parallel plates, with the beam initially travelling straight down the middle. Explain fully what happens to each type of radiation, and why they behave differently, referring to charge, mass and ionising ability.
Complete this alpha decay equation by finding the mass number and atomic number of the daughter nuclide Y:
Potassium-40 () undergoes beta-minus decay to form calcium.
Write the full balanced decay equation, showing your reasoning for both numbers on the daughter nuclide.
A nucleus undergoes a beta-minus decay, and the resulting nucleus then undergoes a further beta-minus decay.
Write both decay equations, and explain fully why two successive beta decays increase the atomic number by 2 while leaving the mass number unchanged throughout.
State what is meant by the half-life of a radioactive isotope.
A radioactive source has an initial count rate of counts per minute. Its half-life is minutes.
Calculate the count rate after minutes, showing your working.
A student measures the count rate of a radioactive sample every 2 minutes and plots a decay curve. She reads the half-life as 6 minutes near the start of the graph, and separately estimates it as 6 minutes again using two points much later in the decay.
Explain fully why she gets the same half-life both times, and describe how she could estimate the half-life from a single reading and the equation instead of using the graph.
Describe what happens during induced nuclear fission of a uranium-235 nucleus.
In a nuclear reactor, explain why control rods are used, and explain what would happen to the reactor's power output if they were withdrawn further.
A reactor uses a moderator and control rods, and its fuel is enriched to increase the proportion of uranium-235. Explain how these three features work together to sustain a controlled chain reaction, linking the role of each to the behaviour of neutrons.
State what nuclear fusion is, and give one example of where it occurs naturally.
Explain why extremely high temperatures are needed for fusion to occur.
Compare fission and fusion as sources of energy for electricity generation, linking the physics of each process to its practical advantages and disadvantages.
A nuclear reaction converts kg of mass into energy.
Calculate the energy released. ( m s−1)
A reactor releases J of energy in one day.
Calculate its average power output, and calculate the mass converted into energy over that day. ( m s−1)
A nuclear power station releases J of nuclear energy in a day but delivers an average electrical output of W.
Calculate the mass converted into energy and the efficiency of the station, and explain, in terms of the energy transformations taking place, why the electrical output is so much smaller than the nuclear energy released. ( m s−1)
State one medical use of radioactivity and name the type of radiation typically used for it.
A thickness gauge uses a beta source on one side of a moving sheet of metal, with a detector on the other side measuring how much radiation passes through.
Explain why beta radiation, rather than alpha or gamma, is the appropriate choice for this application.
Explain fully how carbon dating is used to estimate the age of an object that was once living, referring to the behaviour of carbon-14 before and after the organism's death, and to the half-life equation.
Name two natural sources of background radiation.
A worker in a nuclear facility must handle a strong gamma-emitting source.
Describe two practical ways she can reduce her radiation exposure, explaining why each is effective.
A radioactive source that emits both alpha and gamma radiation is being handled. Explain fully why alpha radiation poses little external risk to a worker standing near the source, but would be very dangerous if the source were accidentally swallowed — while gamma radiation is dangerous in both situations.