Motivations for plum pudding model (advanced)

[Question Man]

Hello!

Is anyone able to direct me to information regarding the motivation of the plum pudding model of the atom (as opposed to a simply a collection of positive and negative charges)?

I am looking for an explanation at the advanced undergrad + level. I recall once reading an explanation in an introductory book, but forgetting it because I was able to recognise that it was a bogus exposition.

 

[Oldfart]

http://en.wikipedia.org/wiki/Plum_pudding_model

 

[SpectraCat]

Your best bet is to try to find a biography of J.J. Thomson somewhere. Or at least an historical account of his cathode ray experiments. I know he formatted his hypothesis of the plum pudding model based on the results of those experiments, but I don't know much beyond what you can easily find on wikipedia and elsewhere.

 

[Question Man]

There is a link on the bottom of the wikipedia page to an excerpt of Thomson's original paper. I have found the whole paper here :

http://www.cond-mat.physik.uni-mainz.de/~oettel/ws10/thomson_PhilMag_7_237_1904.pdf

In it, Thomson seems to show that if the electrons are restriceted to move in various planes whose centers are the center of a uniformly charged shpere, they will find their equilibrium in concentric rings in those various planes.

I cannot infer why he would use a uniform sphere of positive charge rather than a point charge though, other than that he anticipated the former would provide better test implications (about the chemical properties of various atoms, for instance). I may have to wait until I get back to my university to continue investigating, if I have time.