Nuclear fission
The splitting of a heavy nucleus into two smaller fragments (typically near mass numbers around 90 and 140 for uranium-235) initiated by absorption of a neutron. Nuclear fission releases large amounts of energy (≈ 200 MeV per fission) because the binding energy per nucleon increases in the fragments. The fission process releases additional neutrons, potentially initiating a chain reaction.
Formula
²³⁵U + n → fission fragments + ~2–3n + ~200 MeV
Real World
EDF Energy's Hinkley Point C nuclear power station, under construction in Somerset, will use uranium-235 fission chain reactions to generate enough electricity for around six million UK homes.
Exam Focus
Explain energy release by referencing the increase in binding energy per nucleon from uranium to fragments — never just state 'mass is converted to energy' without this context.
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