Before the gold foil experiment people believed the atom resembled a chocolate chip cookie with the chocolate being the electrons. In the experiment there was a lead box that projected a beam of positively charged subatomic particles through a small hole. They were expected to hit the gold foil and bounce off of it and hit the zinc shield that surrounded it. http://www.guardian.co.uk/education/2009/feb/10/rutherford-manchester-university-radiation
Milikin performed the oil drop experiment that discovered the mass of an electron. He measured how strong an applied electric field had to be in order to stop the oil drop from falling. By doing this he could find the gravity applied and thus discovering the mass of the electron was was proven to be 1/1840. However, we now call that 0. http://en.wikipedia.org/wiki/Robert_Millikan
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