E.3.5—Strong nuclear force
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- SL
Model Strong Nuclear Force
Describe the force
The strong nuclear force is attractive between nucleons at nuclear separations and has a very short range. It can bind protons and neutrons despite the electrostatic repulsion between protons.
Explain stability
At short distances the strong force can dominate, while the electromagnetic force is repulsive and long range. A stable nucleus requires the attractive nuclear interaction to overcome proton repulsion within the nucleus.
Keep the range distinction
The strong force does not act as a long-range force between separated nuclei. Its short range is why increasing nuclear size makes stability more difficult.
Common trap
Do not call the strong force repulsive between nucleons in the binding explanation, and do not confuse it with the weak nuclear interaction.
E.3.5 Exam Analysis
Assessment in practice
2–3 marksHow it is assessed
Questions explain why a stable nucleus can exist or classify which fundamental forces act on electrons and quarks.
Command terms
State / Explain
What earns marks
State short range and attractive for the strong force, long range and repulsive for the electromagnetic force, then relate these properties to stability.
Watch for
Giving only the names of forces without their range and sign, or assigning the strong force to electrons.