Protons and neutrons are considered composite particles rather than fundamental particles. They are composed of smaller particles called quarks, which are elementary particles. Quarks are held together by the strong nuclear force to form protons and neutrons.
A proton consists of two up quarks (each with a charge of +2/3) and one down quark (with a charge of -1/3). The combined charges of the quarks give the proton its positive charge (+1). Neutrons, on the other hand, consist of two down quarks and one up quark. The combination of charges in a neutron results in a net charge of 0.
The strong nuclear force, mediated by particles called gluons, acts between the quarks within a proton or neutron, holding them together. This force is responsible for overcoming the electrostatic repulsion between the positively charged quarks within a proton and maintaining their stability.
It's important to note that while quarks are considered elementary particles, protons and neutrons are composite particles made up of these quarks. Therefore, protons and neutrons are not fundamental particles themselves but rather bound states of quarks held together by the strong nuclear force.