The History of the Atomic Model By lgrzina 400 Democritus discovered that everything was composed of atoms Jan 1, 1803 John Dalton discovered that atomsof different elements are different sizes Jan 1, 1897 J.J. Thomson discovered the electron Jan 1, 1911 Ernest Rutherford discovered there is a positively charged center called the nucleus Jan 1, 1913 Niels Bohr discover that there is a positively chraged nucleus surrounded by orbiting electrons Jan 1, 1932 James Chadwick discovered the neutron
