The Development of the Atomic Theory

1
The Development of the Atomic Theory
2
Democritus

• 440 BCE
• Atoms are small, hard particles.
• Atoms are uncuttable.
• Atoms constantly move.

3
Dalton

• 1803
• Atoms of different elements are different.
• He conducted experiments in combining elements.
• Atoms of the same element are exactly alike.

4
Dalton

• 1803
• All substances are made of atoms.
• Elements combine is specific proportions.

5
Thomson

• 1897
• There are small, negatively charged particles
  inside the atom.
• He conducted the cathode-ray tube experiment.
• His theory of atomic structure led to the plum
  pudding model.

6
Rutherford

• 1909
• He conducted the gold foil experiment.
• 1911
• Atoms contain mostly empty space.
• Most of an atoms mass is in the nucleus.

7
Rutherford

• 1911
• There is a small, dense, positively charged
  nucleus.
• Electrons move in the empty space of an atom.

8
Bohr

• 1913
• Electrons travel in definite paths.
• Electrons jump between levels from path to path.

9
Schrodinger and Heisenberg

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

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Name

• Science period
• Anderson