Nuclear size, mass and density from R = R₀A^⅓; mass defect and binding energy per nucleon; and one graph that explains why fusion below iron and fission above it both release energy.
Unit 6 carries 12 of the 50 physics marks — the heaviest unit in the subject — and with seven chapters sharing them, this one averages a little under two (MEC publishes weights by unit, not by chapter). It is also the unit's foundation: the binding-energy curve drawn here is what radioactivity, fission reactors and the Sun all stand on.
The MEC scope lines are: Nucleus: charge, size, mass and density; Mass defect, binding energy per nucleon and Einstein's mass–energy relation; Nuclear fusion and fission. The headings below are those three points, in MEC's order.
Three ways it is asked: recall (the value of R₀, what an isotone is, the conversion 1 u = 931.5 MeV, what a moderator does); understanding (why every nucleus has the same density, why the binding-energy curve peaks near iron, why both fusion and fission give out energy); application (a binding energy per nucleon from atomic masses, a Q-value, the energy from a kilogram of uranium-235, a nuclear radius from a mass number).
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