Compare the nuclide notation $^{234}_{91}\text{Pa}$ with the nuclide notation $^{234}_{92}\text{U}$ and infer what this indicates about what leaves a nucleus of protactinium-234 as it decays to uranium-234. Put a tick (✓) in the relevant boxes of Table 9.1 to show the deductions made from the nuclide notations.
Explain, using their nuclear compositions, why protactinium-231 and protactinium-234 are isotopes of the same element.
Explain, by referring to their nuclear compositions, why protactinium-231 and protactinium-234 are different isotopes of that element.
The teacher measures and records the background radiation count rate. Describe what is meant by ‘background radiation’ and state two major sources of the count rate measured by the teacher.
Suggest one precaution that will allow the sample to be moved safely.
The count rate is measured every 20 s with the sample present, and then corrected for background radiation. Fig. 9.1 shows a graph of the corrected count rate against time for the protactinium-234 sample. The curve is the best-fit line. Explain why many of the crosses do not lie on the curve.
Using Fig. 9.1, determine the half-life of protactinium-234. Show your working.
The uranium-234 made from the protactinium-234 is also radioactive. Its half-life is many thousands of years. Explain why the radiation from uranium-234 does not affect the count rates measured in this experiment.