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5.2.5. Half-life
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 45 questions
Thorium-229 is a radioactive isotope used in several medical applications that involve alpha-particles and beta-particles. During ionisation, a helium atom becomes a helium ion. shows a diagram of a helium (He+) ion. protons neutrons electron State how the structure of a helium atom differs from the structure of the helium ion. State how the structure of an alpha-particle differs from the structure of the helium ion. A nucleus of thorium-229 (229 90 Th) decays by alpha (α) emission to a nucleus of element X. 90 Th X + 4 2α The nucleus of X then decays to a nucleus of Y by beta (β) emission. X Y + 0 –1β Complete Table 9.1 to show the number of protons and neutrons in a nucleus of X and in a nucleus of Y. Table 9.1 nucleus number of protons number of neutrons X Y Experiments can show that a sample of a material is radioactive. Describe the apparatus and the procedure used to show that a sample emits both alpha- particles and beta-particles. You may draw a diagram of the apparatus, if you wish. State what is meant by the half-life of thorium-229. A sample of pure thorium-229 contains 4.0 × 1014 atoms. After 22 000 years, the number of atoms of thorium-229 in the sample is 5.0 × 1013. Determine the half-life of thorium-229. Show your working. half-life =
5054_s22_qp_22
THEORY
2022
Paper 2, Variant 2
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10 An atom of phosphorus (chemical symbol P) is composed of 15 electrons, 17 neutrons and 15 protons. For this atom, state the proton number (atomic number), the nucleon number (mass number). This phosphorus atom is radioactive. As it decays to an atom of sulfur (chemical symbol S), it emits a beta-particle (symbol ). Write a nuclear equation for this decay. Explain what is meant by a beta-particle. A sample of radioactive material contains many of these phosphorus atoms. Describe an experiment to investigate whether the sample emits only beta-particles. A diagram may be included. This isotope of phosphorus has a radioactive half-life of 14.3 days. Explain what is meant by radioactive half-life. A solution containing such phosphorus atoms is used in a medical procedure. When it is prepared, the solution has an activity of 1400 counts / second. The solution cannot be used when its activity falls below 350 counts / second. Calculate the maximum time between preparing and using the solution. time =
5054_w10_qp_21
THEORY
2010
Paper 2, Variant 1
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Questions Discovered
45