In our studies we saw that the nucleus of an atom is composed of protons and neutrons. We know that protons carry positive electrical charges, whereas neutrons do not have charges, that is, they are neutral particles. We have also seen that particles with the same electrical charge exert a repulsive force against each other, whereas charges with opposite signs exert an attractive force against each other.
According to this “rule”, charges of the same sign repel each other. So what is the force that causes protons to stick together inside an atom's nucleus?
In response to this question, we can say that as two protons get closer, the repulsion forces become more and more intense. Let's look at the illustration above. How is it possible for them to stay united at the core?
In a deeper analysis, at the atomic level, we can say that the reason for such an event is that among the protons there is the existence of another type of force, a force different from those we know (gravitational and electrical), with the following features:
It is an attractive force that only exists when the distance (d) separating the protons is such that d ≤ 10-15 m. So we can say that for a distance d ≤ 10-15 m, she is a force more intense than the electric repulsion force.
Today we know this force as nuclear force. Let's do the following thought-only experiment, where we try to approximate two protons, starting from a situation where the distance d becomes equal to 10-15 m, suddenly starts acting the nuclear force, attracting and joining the protons.
The nuclear force also acts between two neutrons, as well as between a proton and a neutron. It is then that guarantees the stability of the core. That's why it's so hard to rip protons and neutrons out of an atom's nucleus. It's easier to rip out electrons, which don't suffer the action of the nuclear force.
By Domitiano Marques
Graduated in Physics
Brazil School Team
Source: Brazil School - https://brasilescola.uol.com.br/fisica/a-forca-nuclear.htm
