GCSE Combined Science (AQA)

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The Plum Pudding Model

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Atomic structure Atoms and isotopes

The Plum Pudding Model

2:15 History of the Atom
Spec 4.4.1.3
Previous Pre-Electron Ideas Next Alpha Scattering
  • In 1897, JJ Thompson observed particles traveling between oppositely charged hot metal plates.
  • The experiment involved two charged plates with a potential difference between them.
  • A small particle released from one plate would move between the plates due to the electrostatic force.
  • The particle could be detected by measuring the change of charge on the plates.
  • These particles were negatively charged and much smaller than atoms.
  • Discovering a particle smaller than an atom was significant as it proved atoms weren't the smallest pieces of matter.
  • Electrons had a negative charge as they were repelled from negative and attracted to positive plates.
  • JJ Thompson discovered electrons.
  • In 1904, Thompson presented a new model for the atom to explain the existence of electrons, known as the plum pudding model.
  • The plum pudding model suggested that atoms contained electrons.
  • The model depicted the atom as a ball of positive charge with negatively charged electrons embedded inside, like plums in a plum pudding.
  • The electrons were evenly spread out within the positive charge.
  • The plum pudding model influenced later experiments looking into the atom.

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