Individual+Models


 * Rutherford-Bohr Model **

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Rutherford had conducted experiments in which he shot relatively large, charged particles ( alpha particles ) at a thin gold foil. He found that most of the particles passed directly through the foil, but some came off at odd angles, as though they had been deflected. From these results, Rutherford concluded that each atom was mostly empty space, but also contained a dense region--a central mass, which his alpha particles could not pass through. He also concluded that this central mass must have a positive charge, to deflect the positively charged alpha particles.  Rutherford and Bohr pictured the arrangement of the atom's parts to look like our solar system. At the center of every atom is a nucleus , which is comparable to the sun in our solar system. Electrons move around the nucleus in "orbits" similar to the way planets move around the sun. The Rutherford-Bohr model provided the first really useful view of the atom. It matched what scientist knew about chemical reactions and the way atoms behaved. It led to some predictions that were later proven correct. Bohr had corrected a serious flaw by recognizing that electrons had to be in orbits (energy states). But his analysis of the energy given off when an electron dropped from a higher energy orbit to a lower energy orbit didn't hold up for atoms bigger than hydrogen (the simplest atom, with only one proton and no neutrons) More work needed to be done on the model. http://www.epa.gov/rpdweb00/understand/rutherford.html