Proton is one of the constituents of an atom, besides neutron and electron. These positively charged protons reside in the nucleus of the atom and add to the overall positive charge of a molecule.
Ernest Rutherford is generally credited with the discovery of protons. He discovered alpha and beta ‘rays’ from uranium in 1899. The alpha rays were later found to be from the nuclei of helium atoms. In 1919 Rutherford conducted many experiments to explore radioactivity. As a result of one of these experiments, he discovered that atoms have a concentrated positive centre charge which contains most of the mass of that atom.
Rutherford suggested that the nucleus carried a positively charged particle. He called it proton; a name derived from the Greek word ‘protos’ which means ‘first’. The numbers of protons differ from one element to another thereby giving each nucleus a different charge. This meant that the hydrogen nucleus, which has a single proton, was an elementary particle.
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