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440
Democritus
Theory from Democritus
440 BCE
*atoms are small, hard particles
*atoms are "uncuttable"
*atoms are made of a single material formed into different shapes & sizes -
Dalton, John
Dalton on wikipedia
*Dalton conducted experiments combining atoms
*all substances are made of atoms
*atoms of the same element are exactly alike
*atoms of different elements are different -
Thomson, J.J.
Plum Pudding Model
*Plum Pudding Model
*small negative charged particles in atoms
*conducted the Cathode-Ray Tube Experiment -
Period: to
Rutherford, Ernest
Gold-Foil Experiment *conducted the Gold-Foil Experiment
*atom has a small, dense, positively charged nucleus
*most of the atom's mass is in the nucleus
*atom contains mostly empty space
*model shows electrons surrounding the nucleus at a distance -
Bohr, Niels
Bohr's Model
*electrons travel in certain paths, or energy levels
*electrons can jump from one energy level to another -
Period: to
Schrodinger & Heisenberg
History of the Atom
Modern Atomic Theory
Atom's Structure
*electron path cannot be predicted
*electrons are found in electron clouds, not paths
