The charges of protons, electrons, and neutrons are determined by their fundamental properties and interactions within the framework of the Standard Model of particle physics. Here's an explanation for each:
Protons: Protons are positively charged particles. They carry a charge of +1 elementary charge. The positive charge of a proton arises from the fundamental property of having an excess of one positive elementary charge compared to its neutral counterpart, the neutron. Protons are composed of three quarks—two up quarks and one down quark—where the up quark carries a charge of +2/3 and the down quark carries a charge of -1/3. The combination of these charges in a proton results in an overall charge of +1.
Electrons: Electrons are negatively charged particles. They carry a charge of -1 elementary charge. The negative charge of an electron arises from the fundamental property of having an excess of one negative elementary charge compared to its neutral counterpart. Electrons are elementary particles and are not composed of smaller particles like protons and neutrons. Their negative charge is an intrinsic property of the electron.
Neutrons: Neutrons are electrically neutral particles. They do not possess any net charge, and their charge is considered zero. Neutrons are composed of three quarks—two down quarks and one up quark—where both down quarks carry a charge of -1/3 and the up quark carries a charge of +2/3. The combination of these charges in a neutron results in an overall charge of zero, making it electrically neutral.
The charges of these particles play a crucial role in the interactions that govern the behavior of matter and the structure of atoms. Protons and electrons interact through electromagnetic forces, while neutrons participate in the strong nuclear force that binds atomic nuclei together.