Nuclear reactions, mass defect and binding energy

Repair the common break

Common misconception: Mass is separately conserved in a nuclear reaction.

Correct model: Conserve nucleon number, charge and mass–energy; convert mass defect with E = mc² and use binding energy per nucleon to explain fusion and fission.

Worked transfer

For a nucleus whose separated nucleons exceed its mass by Δm, binding energy is Δmc². Nuclear reactions conserve charge, nucleon number and total mass–energy, not rest mass by itself.

Guided practice

Explain why “Mass is separately conserved in a nuclear reaction.” fails. Then construct one example that correctly applies nuclear reactions, mass defect and binding energy.

Independent practice

Given a deuteron mass defect of 0.00239 u, calculate its binding energy in MeV using 1 u = 931.5 MeV/c² and state the conserved quantities in its formation.

Return to the recorded repair plan when the explanation and application are secure enough to re-test.