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⚛️ Physics  ·  Nuclei  ·  NEET & JEE

The mass defect in forming a deuteron from a free proton and neutron is 0.00239 u (1 u = 931.5 MeV). Its binding energy is:

Answer: 2.22 MeV.

  • A 8.8 MeV
  • B 4.4 MeV
  • C 1.1 MeV
  • D 2.22 MeV

Correct answer: D. 2.22 MeV

Explanation: Binding energy = Δm × 931.5 = 0.00239 × 931.5 ≈ 2.22 MeV.

Binding Energy per Nucleon vs Mass NumberMass number ABE/nucleonFe-56 (peak, most stable)FUSION region (light → medium)FISSION region (heavy → medium)Both processes release energy by moving nuclei toward the Fe-56 peak

Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.

Concept context

Radioactivity, nuclear reactions, fission, fusion, and binding energy.

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