Atoms By 886099 440 BCE Continuous theory of matter made by Aristotle and Plato, rejecting Democritus's theory and they believed that matter was infinite and divisible 370 BCE Democritus came up with the idea of atoms or "atomos", meaning indivisible particles, this was also the discontinuous model. Democritus came up with the idea of atoms 1804 Dalton atomic theory, which was the first theory that described matter using atoms and their properties such as all atoms had the same mass. 1897 Thomson discovered the electrons in 1897, using the cathode ray experiment in which alpha particles bended towards a negative charge of electricity. 1904 JJ Thomson made plum pudding model of electrons scattered in the positively charged space. 1911 The nucleus of the atom was discovered by Rutherford and the nuclear atom model with neutrons and protons in nucleus were discovered in 1911 1913 Bohr Atomic model was with the electrons orbiting the nucleus was made in 1913 1917 Albert Einstein recognized photons, packets of electromagnetic radiation 1926 Erwin Schrödinger came up with the electron cloud model has dense nucleus with clouds of electrons that move like waves. 1932 Chadwick discovered the Neutron by using scattered data where he found the mass of the neutron in 1932 Chadwick discovered the Neutron 1938 Meitner discovered nuclear fission can produce massive amounts of energy. Nukes 1948 Goeppert-Mayer made the discovery of nuclear shell model for nucleus Discovery of nuclear shell model for nucleus 1964 Quarks are the building blocks of positively or negatively charged atoms.