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460 BCE
Democritus
Theorized all material bodies are made up of atoms. He also developed the concept of the atom. -
Period: 460 BCE to
History of the Atom
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450 BCE
Aristotle
He did not believe in the atomic theory. He believed all materials on Earth were made of the four elements, Earth, Fire, Water, and Air. -
John Dalton
Had the first idea of the atom, Atomic theory: All matter is made of atoms. Atoms are indivisible and indestructible, All atoms of a given element are identical in mass and properties, Compounds are formed by a combination of two or more different kinds of atoms, A chemical reaction is a rearrangement of atoms, and atoms cannot be created or destroyed. -
J.J Thomson
Discovered the electron, Plum Pudding model, Atom was positively charged sphere, small electrons spread throughout. Cathode Ray Tube -
Robert Milikan
Oil Drop Experiment help discover the mass and charge of an electron -
Ernest Rutherford
Discovered the nucleus of the atom and said it was positive. He discovered the proton. Gold Foil experiment. Developed the nuclear model. Discovered that most of the atom is empty space with a really dense middle, which is the nucleus, the electrons are spread out. -
Niels Bohr
Student of Rutherford, expanded on the nuclear model, discovered the electrons orbit the nucleus, Planetary Model. -
James Chadwick
Discovered the neutron, student of Ernest Rutherford, discovered the mass of proton and neutron are close. -
Erwin Schrodinger
Developed the Quantum Mechanical Model, theorized that the electrons don't orbit the nucleus, but that they are in electron clouds.