When was plum pudding model invented

During the s and s, his work largely revolved around developing mathematical models for chemical processes, the transformation of energy in mathematical and theoretical terms, and electromagnetism. This consists of a sealed glass container with two electrodes that are separated by a vacuum. When voltage is applied across the electrodes, cathode rays are generated which take the form of a glowing patch of gas that stretches to the far end of the tube.

Through experimentation, Thomson observed that these rays could be deflected by electric and magnetic fields.

Upon measuring the mass-to-charge ration of these particles, he discovered that they were 1ooo times smaller and times lighter than hydrogen. This effectively disproved the notion that the hydrogen atom was the smallest unit of matter, and Thompson went further to suggest that atoms were divisible. To explain the overall charge of the atom, which consisted of both positive and negative charges, Thompson proposed a model whereby the negatively charged corpuscles were distributed in a uniform sea of positive charge.

And from this, the Plum Pudding Model was born, so named because it closely resembled the English desert that consists of plum cake and raisins. Unfortunately, subsequent experiments revealed a number of scientific problems with the model. Five years later, the model would be disproved by Hans Geiger and Ernest Marsden, who conducted a series of experiments using alpha particles and gold foil.

However, they noted instead that while most shot straight through, some of them were scattered in various directions, with some going back in the direction of the source. Since alpha particles are just helium nuclei which are positively charged this implied that the positive charge in the atom was not widely dispersed, but concentrated in a tiny volume.

In addition, the fact that those particles that were not deflected passed through unimpeded meant that these positive spaces were separated by vast gulfs of empty space. Instead, he proposed a model where the atom consisted of mostly empty space, with all its positive charge concentrated in its center in a very tiny volume, that was surrounded by a cloud of electrons.

Philosophical Magazine 6th series 7 , — Google Scholar. Secondary Literature 6. John Heilbron: J. Thomson and the Bohr atom. Armin Hermann ed. Physik, issue 10 Google Scholar. Klaus Hentschel There are no affiliations available.

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