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Thomson's plum pudding
Beginner
Early atom model with electrons embedded in positive charge.
J.J. Thomson found the electron in 1897 and proposed atoms as a positive sphere with electrons embedded like plums. It explained neutrality but not spectra or scattering.
Cathode rays were deflected by E and B fields to give e/m.
Replaced by Rutherford's model.
In more detail
J.J. Thomson proposed that the atom is a sphere of positive charge with electrons embedded in it, like plums in a pudding. The model was later replaced after scattering experiments.
Real-world uses
- It was an important early step in understanding atomic structure.
- It shows how models change when new evidence appears.
- Historians of science describe Thomson's model as an early step toward discovering the electron inside atoms.
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Frequently asked questions
Why was it called plum pudding?
Because the electrons were thought to be scattered through a positive sphere, like plums in a pudding.
Why was it abandoned?
Rutherford's experiment showed that the positive charge is concentrated in a tiny nucleus.
Why was the plum pudding model abandoned?
Rutherford's scattering experiment showed that most of an atom's mass and positive charge are concentrated in a tiny nucleus.
Related topics in Atomic & Nuclear Physics
Rutherford's scattering experiment · Rutherford model limits · Bohr model