The history of the Atom

• What model of the atom was proposed by J.J. Thomson?


  The plum pudding model
• What did the plum pudding model suggest about the structure of the atom?


  It suggested that atoms are composed of a positively charged sphere with negatively charged electrons embedded in it
• Who first proposed the idea of the atom in ancient history?

  Democritus
• In what year did John Dalton agree with Democritus about the atomic theory?


  1804
• What was the main finding of J.J. Thomson's experiments?


  He discovered that cathode rays could be removed from atoms
• What did Ernest Rutherford's alpha particle scattering experiment involve?


  A beam of alpha particles directed at a thin foil
• What was the expected outcome of the alpha particle scattering experiment based on the plum pudding model?


  That alpha particles would go straight through or be slightly deflected
• What did the results of the alpha particle scattering experiment reveal about atomic structure?


  Atoms must have small, positively charged nuclei at the center
• What conclusions were drawn from the alpha particle scattering experiment?


  • Most of the atom is empty space since most alpha particles passed straight through.
  • The nucleus has a large positive charge as some alpha particles were repelled.
  • The nucleus is small because very few alpha particles were deflected back.
• What did the alpha particle scattering experiment demonstrate about the behavior of alpha particles?


  Some alpha particles were deflected at large angles, while most were not deflected
• What model of the atom was developed as a result of the alpha particle scattering experiment?


  The first nuclear model of the atom
• How does the nuclear model of the atom differ from the plum pudding model?


  The nuclear model has a small, dense nucleus at the center, while the plum pudding model has a diffuse positive charge