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400 BCE
Democritus
First to suggest atoms, stated they were tiny, invisible, and indestructible particles. -
Period: 400 BCE to
History of the Atom
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Period: to
John Dalton
Transformed Democritus’s ideas into a scientific theory. Also agreed all matter was created by atoms. -
Period: to
Max Planck
Began work on the quantum theory. -
Dmitri Mendeleev
Created the first draft of the periodic table. -
Eugene Goldstein
Found evidence for a positively charged particle. Discovered because he observed a cathode-ray tube and saw the rays traveling in an opposite direction of the cathode rays. Found out about protons. -
J.J. Thomson
He was the that discovered the electron, by performing experiments that passed an electric current through glasses at low pressure. -
Ernest Rutherford
Proposed that the atom is mostly empty space. -
Niels Bohr
Created a new theory for the structure of an atom. With this theory you could determine the atom’s chemical properties. -
Robert Millikan
Tried to find that quantity of charge carried by an electron. Managed to calculate the mass of the electron -
Werner Heisenberg
Made the theory of the Uncertainty Principle, where one can never know the location or energy of an electron at the same time. -
James Chadwick
Confirmed the existence of the neutron. -
Erwin Schrodinger
Had dissatisfaction of Bohr’s theory, and believe the atomic spectrum should be determined by a kind of eigenvalue problem
