Within a nucleus, nucleons are subject to two main competing forces.
(1) (a) What are these two forces?
(2) (b) Outline how the two forces compete against each other.
(3) (c) Generally, for the majority of nuclides, which of the two forces remains dominant?
(4) Alpha decay occurs only in nuclei with the largest numbers of nucleons.
(d) Explain why the strong force is not always dominant in nuclides with the largest numbers of nucleons.
(5) Americium-241, 95241Am, an isotope of americium used to demonstrate α-decay, decays into neptunium-237.
(e) Write a nuclear decay equation for the α-decay of americium-241 into neptunium-237.
(6) (f) The following table shows nuclear masses in unified atomic mass units.
Particle
Mass (u)
Americium-241
241.004579
Neptunium-237
236.997020
α-particle
4.001510
(i) Show that this decay is energetically possible.
(ii) Hence, calculate the energy released by the decay process.
(iii) What fraction of the available energy would be expected to be taken away as kinetic energy by the α-particle?
(iv) In fact, the α-particle carries away 5.49 MeV of kinetic energy. Suggest a reason for this.
(7) (g) Show that it is not possible for
(i) the americium nucleus to emit only a proton. Mass of proton =1.00728 u; mass of 94240Pu=240.00211 u.
(ii) the americium nucleus to emit only a neutron. Mass of neutron =1.00867 u; mass of 95240Am=240.00305 u.
(8) (h) Suggest why heavy nuclei almost always decay by α-decay rather than by emitting a single proton or neutron.