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The plum pudding model was the first scientific model of the atom to describe an internal structure. It was first proposed by J. J. Thomson in 1904 following his discovery of the electron in 1897, and was rendered obsolete by Ernest Rutherford 's discovery of the atomic nucleus in 1911.
The Thomson problem is a natural consequence of J. J. Thomson's plum pudding model in the absence of its uniform positive background charge. [ 12 ] "No fact discovered about the atom can be trivial, nor fail to accelerate the progress of physical science, for the greater part of natural philosophy is the outcome of the structure and mechanism ...
Thomson's model is popularly known as the plum pudding model, based on the idea that the electrons are distributed throughout the sphere of positive charge with the same density as raisins in a plum pudding. Neither Thomson nor his colleagues ever used this analogy. It seems to have been a conceit of popular science writers. [54]
To explain the overall neutral charge of the atom, he proposed that the corpuscles were distributed in a uniform sea of positive charge. In this "plum pudding model", the electrons were seen as embedded in the positive charge like raisins in a plum pudding (although in Thomson's model they were not stationary, but orbiting rapidly). [32] [33]
John Dalton's model of the atom, which held that atoms are indivisible and indestructible (superseded by nuclear physics) and that all atoms of a given element are identical in mass (superseded by discovery of atomic isotopes). [13] Plum pudding model of the atom—assuming the protons and electrons were mixed together in a single mass
The plum pudding model of J. J. Thomson also had rings of orbiting electrons. The Rutherford paper suggested that the central charge of an atom might be "proportional" to its atomic mass in hydrogen mass units u (roughly 1/2 of it, in Rutherford's model).
In 1904, Thomson suggested that the atom was a sphere of uniform positive electrification, with electrons scattered through it like plums in a pudding, giving rise to the term plum pudding model. Nagaoka rejected Thomson's model on the grounds that opposite charges are impenetrable.
1904 – J. J. Thomson's plum pudding model of the atom 1904; 1905 – Albert Einstein: Special relativity, proposes light quantum (later named photon) to explain the photoelectric effect, Brownian motion, Mass–energy equivalence; 1908 – Hermann Minkowski: Minkowski space; 1911 – Ernest Rutherford: Discovery of the atomic nucleus ...