alpha scattering

• When was the discovery of electrons made?


  In 1897
• What did the discovery of electrons imply about atoms?

  It implied that atoms have an internal structure and are not indivisible spheres
• What is the name of the new model suggested after the discovery of electrons?


  The Plum Pudding model
• How is the Plum Pudding model described?

  An atom is a ball of positive charge with negative electrons embedded in it
• What experiment did scientists conduct to test the Plum Pudding model?

  The alpha scattering experiment
• Why is the alpha scattering experiment considered important?

  It radically changed the way we think about atoms
• What material did scientists use for the alpha scattering experiment?

  Gold foil
• Why did scientists choose gold for the experiment?

  Because it can be hammered into very thin foil just a few atoms thick
• What are the particles fired at the gold foil in the alpha scattering experiment called?

  Alpha particles
• What is a key fact about alpha particles?

  Alpha particles have a positive charge
• What did scientists conclude from the fact that most alpha particles passed straight through the gold foil?


  Atoms are mainly empty space
• What did the deflection of some alpha particles indicate?

  The center of the atom must have a positive charge
• What does it mean if an alpha particle bounces straight back off the gold foil?


  The center of an atom must contain a great deal of mass
• What do we call the central part of an atom?

  The nucleus
• How did the results of the alpha scattering experiment affect the Plum Pudding model?


  It led to the replacement of the Plum Pudding model with the nuclear model
• What are the key features of the nuclear model of atomic structure?

  • Most of the atom is empty space
  • A tiny positive nucleus at the center
  • The nucleus contains most of the mass of the atom
  • Negative electrons are located around the edge of the atom