4.1 Experimental facts
  4.1.1 mass spectrograph
 4.2 Interpretation
 4.3 Deeper analysis of nuclear masses
 4.4 Nuclear mass formula
 4.5 Stability of nuclei
  4.5.1 $\beta$ decay
 4.6 properties of nuclear states
  4.6.1 quantum numbers
  4.6.2 deuteron
  4.6.3 Scattering of nucleons
  4.6.4 Nuclear Forces