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An atom with seven electrons arranged in a pentagonal dipyramid, as imagined by Thomson in 1905. The plum pudding model is an obsolete scientific model of the atom.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 ...
The prevailing model of atomic structure before Rutherford's experiments was devised by J. J. Thomson. [2]: 123 Thomson had discovered the electron through his work on cathode rays [3] and proposed that they existed within atoms, and an electric current is electrons hopping from one atom to an adjacent one in a series.
His mother, Emma Swindells, came from a local textile family. His father, Joseph James Thomson, ran an antiquarian bookshop founded by Thomson's great-grandfather. He had a brother, Frederick Vernon Thomson, who was two years younger than he was. [6] J. J. Thomson was a reserved yet devout Anglican. [7] [8] [9]
Thomson's model was incomplete, it could not predict any of the known properties of the atom such as emission spectra or valencies. In 1906, Robert A. Millikan and Harvey Fletcher performed the oil drop experiment in which they measured the charge of an electron to be about -1.6 × 10 −19 , a value now defined as -1 e .
[1]: 13 Between 1904 and 1910 Thomson developed formulae for the deflection of fast beta particles from his atomic model for comparison to experiment. Similar work by Rutherford using alpha particles would eventually show Thomson's model could not be correct. [2]: 269 Also among the early models were "planetary" or Solar System-like models.
[4] [5] In it, Thomson developed a mathematical treatment of the motions of William Thomson and Peter Tait's atoms. [6] When Thomson later discovered the electron (for which he received a Nobel Prize), he abandoned his "nebular atom" hypothesis based on the vortex atomic theory, in favour of his plum pudding model.
With Thomson's discovery of the electron in 1897, scientist began the search for a model of the interior of the atom. Thomson proposed negative electrons swimming in a pool of positive charge. Between 1908 and 1911, Rutherford showed that the positive part was only 1/3000th of the diameter of the atom. [6]: 26 Models of "planetary" electrons ...