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Atomic Theories

Published on Nov 19, 2015

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PRESENTATION OUTLINE

MODERN THEORY - 20TH CENTURY

  • Electrons are found in electron clouds, not paths.
  • Electrons paths cannot be predicted.

BOHR - 1913

  • Electrons travel in definite paths.
  • Electrons jump between levels from path to path.

RUTHERFORD - 1911

  • Most of an atom's mass is in the nucleus.
  • He conducted the gold foil experiments.
  • Atoms contain mostly empty space.
  • Electrons move in empty space in the atom.
  • There is a small, dense, positively charged nucleus.

THOMSON - 1897

  • His theory of atomic structure led to the "plum-pudding model.
  • He conducted the cathode-ray tube experiment.
  • There are small, negatively charged particles inside an atom.

DALTON - 1803

  • Elements combine in specific proportions.
  • He conducted experiments in combining elements.
  • Atoms of the same element are exactly alike.
  • Atoms of different elements are different

DEMOCRITUS - 440 B.C.

  • All substances are made if atoms.
  • Atoms are small, hard particles.
  • Atoms constantly move.
  • Atoms are "uncuttable."