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430 BCE
Democritus
Democritus brought the theory that matter is made of atoms separated by empty space where atoms move through. -
John Dalton
John Dalton proposed that all matter was composed of atoms and that all atoms of an element were identical and atoms of other elements varied in mass and size. -
Dmitri Mendeleev
Discovered that when the elements were arranged based on the atomic weight it resulted in a table with a recurring pattern. The periodic table -
Eugene Goldstein
Goldstein discovered the proton -
J.J Thomson
J.J Thomson discovered the electron and proposed the atom as a sphere of positive matter with electrons in positions based on electrostatic forces. -
Max Planck
Discovered that energy was always emitted in tiny packets called a quantum of energy. He started a new field called quantum mechanics. -
Robert Millikan
He determined the electric charge of a single electron. -
Ernest Rutherford
Ernest rutherford postulated the nuclear structure of the atom. -
Niels Bohr
Bohr suggested that electrons move around the nucleus in a fixed orbit and if electrons change orbit it results in radiation. -
Erwin Schrödinger
Erwin Schrödinger proposed the quantum mechanical model of the atom which treats electrons as matter waves. -
Werner Heisenberg
Discovered the uncertainty principle, which means that an electron's position and momentum can not both be known at the same time. -
James Chadwick
James Chadwick is responsible for discovering the neutron.