5. Nuclear physics
A section of Physics, 5054
Listing 10 of 279 questions
All the isotopes of the gas radon are radioactive. State one similarity and one difference between the nuclei of two different isotopes of radon. similarity difference The isotope radon-222 decays by alpha-particle emission to an isotope of polonium (Po). The proton number (atomic number) of polonium is 84. Determine the number of neutrons in an atom of the polonium isotope. number of neutrons = Determine the number of protons in an atom of radon-222. number of protrons = Describe how a neutral atom of helium ( 4 2He ) differs from an alpha-particle. In an experiment to collect a small quantity of helium, a sample of radon-222 is enclosed in an inner glass tube which has a very thin wall. shows that this tube is placed inside a container that is initially evacuated. inner glass tube vacuum container seal radon-222 Both the container and the inner glass tube are sealed. As the radon-222 decays, alpha-particles pass through the thin wall of the inner glass tube. shows how the total number of alpha-particles produced by the radioactive decay of the radon-222 changes as time passes. time / days number of alpha-particles 1.0 × 1010 2.0 × 1010 3.0 × 1010 Use to determine the number of alpha-particles produced in 7.6 days. Initially, there are 2.8 × 1010 atoms of radon-222 in the inner glass tube. As each radon- 222 atom decays, it produces an alpha-particle. Calculate the number of radon-222 atoms that remain after 7.6 days. number of atoms remaining = Using the number of radon-222 atoms present initially and the number present after 7.6 days, calculate the half-life of radon-222. half-life = The alpha-particles become helium atoms which are collected in the vacuum shown in . Explain, in terms of the properties of alpha-particles, why the wall of the inner glass tube must be extremely thin. In some parts of the world, radon-222 accumulates in the air in buildings and is breathed in by people. Explain why the presence of an alpha-emitter in the lungs is particularly hazardous.
5054_w19_qp_22
THEORY
2019
Paper 2, Variant 2
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An atom consists of electrons surrounding a nucleus made up of protons and neutrons. State which of these particles have an equal and opposite charge, have almost equal mass. The nuclide notation for carbon-14 is 14 6C. Carbon-14 decays by beta emission to a stable isotope of nitrogen (N). Write numbers in the empty boxes below to show the nuclide notation for this isotope of nitrogen. 6C N + β The half-life of carbon-14 is 5700 years. A sample of wood from a living tree contains 2.4 × 1012 atoms of carbon-14. A similar sample of the same size is taken from an old piece of wood. It contains 6.0 × 1011 atoms of carbon-14. Calculate the age of the old piece of wood. age =
5054_s14_qp_22
THEORY
2014
Paper 2, Variant 2
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11 Complete the table of . type of radiation nature of radiation charge alpha-particle two protons and two neutrons positive beta-particle gamma-ray Technetium-99 is a radioactive isotope that emits gamma-rays and it has a half-life of 6.0 hours. In a hospital, a solution containing this isotope is injected into a patient. The solution travels around the body and the isotope attaches to cancer cells. A few hours after the injection, an instrument is used to detect the gamma-rays emitted by the isotope. A high reading on the instrument indicates the position of cancer cells. Explain what is meant by half-life. Explain why an isotope emitting gamma-rays is used rather than an isotope emitting alpha-particles. Explain why using an isotope with a half-life of 6 hours is better than using an isotope with a half-life of 6 minutes. Explain why using an isotope with a half-life of 6 hours is better than using an isotope with a half-life of 6 days. A different radioactive isotope used in hospitals has a half-life of 13 hours. A sample of this isotope and a detector are placed in a lead box. The count rate is recorded every minute for three minutes. The values obtained are 3202, 3140 and 3258 counts per minute. Explain why the three readings are not the same. Estimate the time taken for the average count rate to fall to 200 counts per minute. time taken = The sample and the detector are taken out of the lead box. The count rate rises slightly because of background radiation. State one cause of background radiation.
5054_s10_qp_21
THEORY
2010
Paper 2, Variant 1
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A hospital laboratory uses a small sample of a radioactive isotope of iodine, 13 3I. Describe the structure of the nucleus of an atom of this isotope. The sample is radioactive. Describe what happens in radioactive decay. The count in one minute from the source is measured several times. shows the readings obtained. Suggest why the readings are different. The half-life of 131 53I is 8.0 days. Estimate the count in one minute obtained from the sample after 24 days. count =
5054_s14_qp_21
THEORY
2014
Paper 2, Variant 1
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Questions Discovered
279