The binding energy of an assembly of particles is the energy required to separate the particles. It is calculated from the internal energies and masses, using the Einstein relationship E = mc², applied separately to the assembly and its constituents. The result in a mass defect : the assembly is lighter than its constituents. In the case of a nucleus, the mass defect is about 1%. Translating masses into energies by multiplying by the square of the speed of light (300 000 km/s, a huge number), this leads to binding energies of around 8 million electronvolts per nucleon. In the fission of uranium nuclei, a fraction of this impressive hidden energy is released.
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E = mc² : mass or internal energyBack to glossary