-
300
Aristotle
Dismissed Democritus’ atom as “worthless.” Said that the four elements were earth, fire, air and water -
400
Democritus
Viewed electrons as a cloud and introduced wave mechanics as a model for the atom -
John Dalton
Father of modern atomic theory; five parts of his atomic theory including that elements are composed of atoms and that element’s atoms are identical in mass. -
J.J. Thomson
Discovered the electron -
Ernest Rutherford
Said that an atom has a small positive nucleus and the remainder is empty space through the gold foil experiment -
R.A. Milikan
Determined the charge and mass of an electron through the oil drop experiment -
Henry Moesley
He stated that the atomic number of an element is equal to the number of protons in the nucleus. -
Niels Bohr
Predicted that electrons travel in specified energy levels. -
Erwin Schrodinger
He was the first person to identify the possibility of an atom. -
Louis de Broglie
Worked with Einstein to determine that electrons were similar to particles and waves -
Werner Heisenberg
Came up with the “uncertainty principle”, which stated that it is impossible to determine the position and momentum of a particle at the same time. -
James Chadwick
Discovered the neutron
