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Thomson's Gold Foil Experiment

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Atoms was not a miraculous discovery it took a long time and many scientists ideas for our understanding of atoms to get this far. The ideas from the following scientists that helped this discovery are Democritus, John Dalton, J.J. Thomson, Ernest Rutherford, James Chadwick/Irene Curie, Niels Bohr, and ending with with the quantum model. Around 400 B.C. Democritus believed after hearing a guy named Leucippus he came to the conclusion that there had to be a basic building block for all matter. Democritus also believed that the atom is the smallest particle of matter. He states that is you keep on cutting a element in half and you can't cut it in half again without it becoming another substance that is a atom. Democritus did not have enough …show more content…
Rutherford thought that if Thomson's model was correct then the mass of the atom was spread out in the atom. Then, if he shot high velocity alpha particles at an atom then there would be very few particles to deflect the alpha particles. He decided to test this with a thin film of gold atoms. As expected, most of the alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly back. These deflections were not consistent with Thomson's model. Rutherford was forced to discard the model and logically concluded that the only way the alpha particles could be deflected backwards was if most of the mass in an atom was concentrated in its nucleus. He thus developed the planetary model of the atom that put all the protons in the nucleus. He put the electrons orbiting around the nucleus like planets around the …show more content…
The movement of the electrons that are in the Rutherford model were unstable because, according to classical mechanics and the electromagnetic theory, any charged particle moving on a curved path emits electromagnetic radiation. This stating the electrons would lose energy and spiral into the nucleus. To remedy the stability problem, Bohr made minor changes to Rutherford model by requiring that the electrons move in orbits of fixed size and energy. The energy of an electron counts on the size of the orbit and is lower for smaller orbits. Radiation can occur only when the electron moves from one orbit to another. The atom will be completely stable in the state with the smallest orbit, since there is not any orbit of lower energy into which the electron can jump.

The quantum mechanical model is proposed by Erwin Schrödinger and is based on quantum theory, which says matter also has properties connected with waves. According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. This is called the Uncertainty Principle. The quantum mechanical model of the atom uses complex shapes of orbits sometimes called electron clouds, volumes of space in which there is likely to be an electron. So, this model is based on probability rather than

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