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Ruthorford's Atomic Theory!
Rutherford's experiment and conclusions were later refined by a physicist, Neils Bohr, in 1913. Their ideas were merged together to form the Rutherford-Bohr model of the atom. This model had a center, nucleus, with electrons orbiting around it. Rutherford's theory and model of the atom are still the basis of what we use today. His model laid the foundation for all atomic and nuclear developments and theories now and in the future. (Site 1 and Site 3).
Rutherford wanted to test Thompson's theory. His plan was simple: fire a beam of alpha particles (small, fast moving, positively charged particles- later known as helium nucei) at a thin sheet of gold foil. His theory was that all the particles would pass through the foil. He also believed that at least some of the particles would come through the foil at minor angles because of the positive charge throughout. He believed they would just be moved a few degrees. The positive charge was spread out all throught the atoms in the gold foil so it was not too strong to deflect them (this was Thompson's theory)(Site 1). Geiger and Marsden tried the experiment in Rutherford's lab in 1909 under his supervision (Site 3).
Geiger and Marsen set up a particle emitter (a ray of particles beams from it), a small sheet of gold foil, and a detecting screen in a circle around the foil with a small slit for the particles to enter in. They conducted the experiment and were suprised with their findings. The majority of the particles (about 7999 out of 8000) would pass through like they hypothesized, but a few (about every 1 out of 8000) would bounce back at major angles, some even right back at the ray. The angles at which the few deflected were sometimes as great as 180 degrees. (Site 1 and Site 3). This led to some different conclusions about the atom. Rutherford, Geiger and Marsden concluded that Thompson's plum pudding or currant bun model was incorrect. The particles only bounced off the foil in certain regions, so Rutherford, Gieger and Marsden concluded that the atom must have a center that is more dense than the rest of the atom. They believed that the center of the atom was more concentrated and contained most of the mass of the atom. Because the majority of the particles went straight through as hypothesized, Rutherford deduced correctly that the rest of the atom was empty space. Rutherford discovered that an atom had ''a central charge'' (later known as an atom) (Site 1).
At the time, the leading theory on atoms was of J.J. Thompson. According to his theory, atoms were built along the lines of currant buns (a form of bread). His model of an atom was similar to the bun. The bun itself was a sphere of spread out positive charge. The currants (little things inside of the bun, kind of like a raisin) were negatively charged electrons spread all throughout. The positives and negatives pretty much canceled themselves out, leaving the atom relatively nuetral. This theory came into play with the gold foil in the experiment (Site 3). This theory is also known ask the plum pudding theory.
In 1909, a man named Ernest Rutherford had a lab at the University of Manchester. Two researchers, Hans Gieger and Ernest Marsden, in his labratory decided to perform an experiment test one of Rutherford's theories (Site 4).
Site one: http://www.ehow.com/about_4569065_rutherfords-gold-foil-experiment.html
Site two: (pictures came from) http://www.rsc.org/chemsoc/timeline//pages/1911.html
Site three: http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html
Site four: http://en.wikipedia.org/wiki/Geiger–Marsden_experiment
Site five: (picture on the bottom)
Site six: youtube for the video!
In the center is the nucleus with electrons orbitting around.
This is a video that totally explains the experiment. Watch it!