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Atomic & Nuclear Physics · Part 3 of 5
6 exam-style questions with model answers, plus 8 quick multi-choice questions — every question on this part of the standard, grouped by the 2 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
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.