A proton is a subatomic particle that has a positive charge of +1 e. An "e" is defined as the elementary electrical charge that a proton possesses, measured at approximately 1.6 x 10^-19 coulombs. The positive electrical charge of a proton is opposed by negative charge of an electron.
The discovery of the existence of the proton and its electrical charge occurred in related experiments conducted by British scientist Ernest Rutherford in 1917, first reported in 1919. Rutherford studied the interaction of nitrogen gas with positive helium ions, which produced what he determined were hydrogen ions. He concluded that hydrogen ions were the basic building blocks of all matter, and, after a meeting in 1920 with the British Association for the Advancement of Science, termed the new particle a proton.