Nuclear instabilityAQA A-Level Physics: Mind map

Exam questions on Nuclear instability

1. Stable nuclei lie in a narrow band on a graph of neutron number N against proton number Z. For light nuclei the band follows the line N = Z, and for heavier nuclei it curves towards larger values of N than Z. Nuclei that lie outside the band are unstable and decay.
   Uranium-238 is a heavy nucleus which decays by alpha emission. Explain, using the graph, why alpha emission suits heavy nuclei and what effect it has on N and Z.2 marks
2. Potassium-40 (⁴⁰₁₉K) is a radioactive isotope found in rocks and in the human body. It decays in two ways: by β⁻ emission to calcium-40, and by electron capture to argon-40.
   Write a balanced equation for the electron capture of potassium-40 to argon-40.2 marks
3. Technetium-99m (⁹⁹ᵐTc) is a source of gamma radiation used in medical diagnosis. It is produced in a hospital by the decay of molybdenum-99, and the technetium-99m nucleus is left in an excited state that decays to the ground state of technetium-99 by emitting a single gamma photon of energy 140 keV. The half-life of technetium-99m is 6.0 hours.
   Calculate the wavelength of the gamma photons emitted by technetium-99m.3 marks