A proton is a subatomic particle, symbol p or p+, with a unitary electric charge of +1e. The rest mass of the proton is 1.6726231×10−27 kg, about 1836 times that of an electron. Protons and neutrons are collectively referred to as “nucleons”. Since 1918, protons have been known to be positively charged particles found in the nucleus of every atom. In 1932, James Chadwick discovered the neutron with no net electric charge but a mass slightly more significant than the proton.
The number of protons in an atomic nucleus defines to what chemical element the atom belongs: each element has one or more characteristic numbers (called “atomic numbers”) of nucleon counts (protons for elements with atomic number Z > 82). For example, carbon has six protons in its nucleus; thus, it is assigned an atomic number Z = 6), whereas uranium contains 92 nuclei and has Z = 92.