The Mass Defect

Show/Hide Sub-topics (Nuclear Physics | A Level Physics)
  1. The ɑ-particle Scattering Experiment
  2. Simple Model of The Atom
  3. Atomic Mass
  4. Mass-energy Relation
  5. The Mass Defect
  6. Binding Energy
  7. Binding Energy Per Nucleon And Nuclear Stability
  8. Nuclear Reactions
  9. Nuclear Fission
  10. Nuclear Fusion
  11. Radioactivity & Radioactive Decay
  12. Characteristics Of Alpha/Beta Particles & Gamma Rays
  13. Activity, Half-life And Decay constant
  14. Effects of Radiation On Living Organism
  15. Geiger-Muller Tube/Counter


The mass defect of a nucleus is defined as the difference between the mass of the separated nucleons and the combined mass of the nucleus.

To calculate the mass defect ΔM for a nucleus that has A protons and B neutrons:
ΔM = Amp + Bmn – Mn, where
mp = mass of a proton
mn = mass of a neutron
Mn = mass of the nucleus

To calculate the mass defect of a neutral(number of proton = number of electron) whole atom ΔMa:
ΔMa = Amp + Bmn + Ame – Ma, where
me = mass of an electron
Ma = mass of the neutral atom


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