-
350
Aristotle
Aristotle – 350 BC – opposed the idea of “atomos”/an atom; believed that only four elements existed: Water, Earth, Fire, Air -
400
Democritus
Democritus – 400 BC – first proposed the existence of “atomos” - an indivisible particle -
John Dalton
Dalton – 1803 – proposed the Atomic Theory -
Marie Curie
Curie – 1898 – explored radioactivity which later contributed to the atomic model -
J.J. Thomson
Thomson – 1904 – discovered the electron -
Albert Einstein
Einstein – 1905 – proved the existence of atoms and introduced relativity -
Robert Millikan
Millikan – 1909 – proved that the electron was 1000 times smaller than the atom -
Ernest Rutherford
Ernest Rutherford – 1910 – proposed existence of the nucleus with his Gold Foil Experiment -
Niels Bohr
Niels Bohr – 1913 – proposed electron energy levels and orbits -
Louis de Broglie
De Broglie – 1924 – postulated the wave nature of electrons and suggested that all matter has wave properties. -
Ernst Schrodinger
Schrodinger – 1926 – explained movement of an electron in an atom as a wave -
Werner Heisenberg
Heisenberg – 1926 – developed the fundamental principle on which quantum mechanics is based on -
James Chadwick
Chadwick – 1932 – discovers neutrons
