"Four Force" Model


The Strong Nuclear Force keeps the parts of the nucleus together. It acts over a very short range and can be both attractive & repulsive.

  • It gives rise to short range attraction between adjacent nucleons, up to a distance of about 3 x 10-15m. (or 3 femtometers).

  • It also gives rise to very short range repulsion below 0.5 x 10-15m(or 0.5 femtometers).


The Electromagnetic Force holds atoms and molecules together. It is also responsible for giving things strength, shape, and hardness.


Weak Nuclear Force

Beta decay can't be explained by the strong nuclear force, the force that is responsible for holding the atomic nucleus together, because this doesn't affect electrons. It can't be explained by the electromagnetic force, because this does not affect neutrons, and the force of gravity is far too weak. Since the new atomic force isn't as strong as the strong nuclear force, it's called the weak nuclear force.


The Gravitational Force is a force that attracts any object with mass. Every object exerts gravitational force upon each other.