The Proton

The proton is an elementary particle found in the nucleus of an atom. Its quark composition is uud or up, up, down. The charges of these quarks add (up=+2/3 up=+2/3 and down=-1/3) to +1, which is why the proton is positively charged. After the discovery of the electron, a positively charged particle was theorized to balance the atom. It interacts with all four forces (gravity, electromagnetism, weak nuclear force, and the strong nuclear force) and it is the second-heaviest particle in the atom (just short of the neutron). The proton is the only member of the Hydrogen nucleus and the number of protons in an atom determines atomic number. Protons are very well-known particles.