Ernest Rutherford is most noted for his famous gold foil experiment. In his experiment, he used radium to produce alpha rays, which were projected on to a piece of gold foil. Behind the foil, there was a detection screen where he wouldbe able to see the alpha particles impact.
This determined that there must be some form positively charged matter must scatter the particles. He also inferred that atoms were mostly empty space, and that electrons orbited the positive center, much like planets around the sun.