Physics > Advanced Modern Physics > 4.0 Nuclear binding energy
Advanced Modern Physics
1.0 X-Rays
2.0 Moseley's Law.
3.0 Nuclear Structure
4.0 Nuclear binding energy
4.1 Binding energy per nucleon
4.2 Variation of Binding energy per nucleon with mass number
4.3 Nuclear stability
5.0 Radioactivity
6.0 Radioactive decay law
4.3 Nuclear stability
4.2 Variation of Binding energy per nucleon with mass number
4.3 Nuclear stability
In nucleus the large electrostatic force between the protons is neutralized by short-range strong nuclear force operating between all the nuclear particles.
The strong nuclear force is stronger than the coulomb repulsive force within nuclear distances.
The strong nuclear force is nearly independent of charge.
In other words, the nuclear forces associated with the proton-proton, proton-neutron, and neutron-neutron interactions are approximately the same.
Light nuclei are most stable if they contain equal number of protons and neutrons ($N$=$Z$) but heavy nuclei are more stable if $N$>$Z$.
This is because as the number of protons increase, the strength of coulomb force also increases, which tend to break the nucleus apart.
As a result, more neutrons are needed to keep the nucleus stable, because neutrons experience only the attractive nuclear forces. In effect, the additional neutrons dilute the nuclear charge density.
However after $Z$=83, these repulsive forces cannot be compensated by addition of more neutrons, making the nuclei unstable.
