Discovered by Ernest Rutherford in 1918). it is a positively charged particle to be found in an atomic nucleus. The number of protons in a nucleus gives the atomic number of an element, the latter being found in the periodic table of elements. A proton has a charge +1 that is the exact opposite of that contained by an electron, -1, and the mass of a proton is 1,826 times greater than that of electron. In the past, the proton was considered to be the most elementary particle until the discovery of the quark.