Models - Note-A-Rific: Models Playing with Models Line...

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Note-A-Rific: Models Playing with Models Line Spectra Bohr’s Model Playing with Models By the year 1900, most scientists had accepted that matter is made up of atoms. Millikan had shown every atom had electrons in it, but also knew that atoms are much heavier than electrons alone, and have neutral charge. J.J. Thomson put forward his “plum pudding model” of the atom (positively charged sphere with little negative charges stuck in it). Ernest Rutherford believed that a better model was possible. He set up an experiment (started at McGill University in Ontario) where he shot α rays at a thin sheet of gold foil. Thought that the positive charge was spread out a lot in the atom… so, he expected to see the α rays travel straight through. Most α rays did go straight through but some α rays scattered… a lot! Some actually came flying back. It was as if they had encountered a high concentration of positive charge. Rutherford’s “planetary” (a.k.a. “nuclear”) model predicted that… All of the positive charge was concentrated in a very tiny nucleus. Orbiting around this nucleus in circles are the electrons. (if they weren’t moving in an orbit, they would be attracted to the nucleus and move straight to it) Most of an atom is empty space! In fact, if the nucleus was the size of a basketball, the nearest electron is over three kilometres away! But there are problems with Rutherford’s model… According to Maxwell, any accelerating charge will generate an EM wave o This EM wave would be a release of energy and give off light at all sorts of wavelengths. If the electron is releasing energy, it should slow down and eventually spiral into
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This note was uploaded on 02/29/2012 for the course PHYS 227 taught by Professor Rabe during the Fall '08 term at Rutgers.

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Models - Note-A-Rific: Models Playing with Models Line...

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