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430
B.C.E. Democritus
Democritus found that...
-Atoms are small,hard,particles
-Atoms are uncuttable
-Atoms are made of a single material formed into differnet shapes and sizes. -
430
Democritus Atomic Model
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John Dalton
John Dalton concluded that...
-Atoms of different elements are different
-Atoms of the same element are exactly alike
-All subtances are made of atoms
He also conducted experiments in combining elements and wanted to know why elements combine in specific proportions. -
Dalton's Atomic Model
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J.J. Thomson
J.J. Thomson found that...
-There are small, negatively charged particles inside an atom
-His theory of atomic structure led to the "plum-pudding" model
He conducted the cathode-ray tube experement. -
Thomson's Atomic Model
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Rutherford
Rutherford found...
-Most of an atoms mass is in the nucleus
-Electrons travel in certain paths or energy levels
-He conducted the Gold Foil experiment
-There is a small,dense, positively charged nucleus
-atoms contain mostly empty space
-His model had electron surrounding the nucleus at a distance -
Rutherford's Atomic Model
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Bohr
Bohr found that...
-Electron can jump from a path in one level to a path in another level -
Bohr's Atomic Model
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Werner Heisenberg and Erwin Schrodinger
Heisenberg and Schrodinger thought that...
-electron paths cannot be predicted
-electrons are found in electron clouds, not paths -
Heisenberg & Schrodinger's Atomic Model
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James Chadwick
Chadwick discovered...
-another particle in the nucleus of atoms
-the neutral neutron -
Chadwick's Atomic Model
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Twentieth Century
We still think Chadwick's atomic model is accurate. Now, we are working in labs with nuclear fission.
