Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
J.J. Thomson was a British physicist who discovered the electron and proposed the 'plum pudding' model of the atom. His work laid the foundation for modern atomic theory.
5 Must Know Facts For Your Next Test
J.J. Thomson discovered the electron in 1897 using a cathode ray tube experiment.
He measured the charge-to-mass ratio of electrons, establishing that they were much lighter than atoms.
Thomson proposed the 'plum pudding' model, which suggested that electrons were embedded in a positive 'pudding-like' substance.
His discovery challenged the prevailing view that atoms were indivisible particles.
Thomson's work led to further experiments by other scientists, ultimately leading to the development of more accurate atomic models.
A subatomic particle with a negative charge and negligible mass compared to protons and neutrons.
Cathode Ray Tube: An experimental apparatus used by J.J. Thomson to discover electrons; it emits rays when high voltage is applied between two electrodes.
'Plum Pudding' Model: An early atomic model proposed by J.J. Thomson where electrons are scattered within a positively charged 'pudding-like' substance.