Physics · Unit 1 · Ionising radiation and nuclear reactions · Nuclear model and stability
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A helium-4 nucleus has a mass of 4.0015 u, which is less than the combined mass of its constituent protons and neutrons (4.0330 u). Describe the mass–energy equivalence relationship and explain what happens to the missing mass.
A deuterium nucleus (²H) has a mass of 2.014102 u. It contains one proton (mass 1.007276 u) and one neutron (mass 1.008665 u). Describe the mass–energy equivalence relationship and explain how it accounts for the difference between the measured mass of the deuterium nucleus and the combined mass of its constituent nucleons.
In a fusion reactor, two deuterium nuclei (each with mass 2.014 u) combine to form a helium-3 nucleus (mass 3.016 u) and a neutron (mass 1.009 u). The atomic mass unit is 1 u = 1.661 × 10⁻²⁷ kg. Describe how the mass–energy equivalence relationship applies to this reaction.