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Thomson atomic model
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Diagram of the Thomson atomic model showing a sphere of positively charged matter with embedded electrons represented as small circles inside the larger orange sphere.
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J.J. Thomson
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atom
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Diagram of the Thomson atomic model showing a sphere of positively charged matter with embedded electrons represented as small circles inside the larger orange sphere.
Thomson atomic model Lord Kelvin envisioned the atom as a sphere with a uniformly distributed positive charge and embedded within it enough electrons to neutralize the positive charge. This model was further supported by J.J. Thomson's subsequent discovery of the electron.

Thomson atomic model

physics
Also known as: “plum pudding” atomic model, Thomson model
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History

Thomson atomic model, earliest theoretical description of the inner structure of atoms, proposed about 1900 by William Thomson (Lord Kelvin) and strongly supported by Sir Joseph John Thomson, who had discovered (1897) the electron, a negatively charged part of every atom. Though several alternative models were advanced in the 1900s by Kelvin and others, Thomson held that atoms are uniform spheres of positively charged matter in which electrons are embedded. Popularly known as the plum pudding model, it had to be abandoned (1911) on both theoretical and experimental grounds in favour of the Rutherford atomic model, in which the electrons describe orbits about a tiny positive nucleus. See also atomic model.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Melissa Petruzzello.