Protons are composite particles made up of smaller particles called quarks. Specifically, a proton consists of three quarks bound together by the strong nuclear force. The quarks that make up protons are known as up quarks (two up quarks) and a down quark.
The up quark has a charge of +2/3 elementary charge, while the down quark has a charge of -1/3 elementary charge. The combination of two up quarks with a charge of +2/3 each and one down quark with a charge of -1/3 results in a net charge of +1 for the proton.
The strong nuclear force, mediated by particles called gluons, acts as the binding force between the quarks within the proton. This force is responsible for holding the quarks together and giving the proton its stability.
It's important to note that while quarks are the fundamental constituents of protons, they cannot exist as isolated particles due to a property called confinement. Quarks are always found in composite particles like protons or neutrons and are never observed as free individual particles in isolation.
In addition to the three quarks, protons also contain a sea of virtual quark-antiquark pairs and gluons that continuously appear and disappear due to the quantum fluctuations of the strong force. These fluctuations contribute to the overall properties of the proton but are not considered as the primary building blocks.
To summarize, protons are composed of three quarks—two up quarks and one down quark—held together by the strong nuclear force. The combination of these quarks and the interactions between them gives rise to the properties and characteristics of the proton.