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This model showed us what you get when you get something so small it can't be divided any further. It provided a basic explanation of the basic unit of matter. This man was a philosopher & therefore did no experimentation.
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Aristotle explained in an easily understandable way that all objects must be made up of one of 4 things: Air, Fire, Earth, or Water. (i.e. if it's wet it's made of water). No experimentation was done as Aristotle was a philosopher & philosophers don't work w/ their hands.
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John Dalton presented his atomic theory which generally said elements are made of microscopic atoms ; atoms which can't be created or destroyed, but can be combined/seperated from compounds. He also came up with the Law of Multiple Proportions. He experimented with such things as water, ammonia, & hydrogen.
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This man performed experiments with a photographic plate & 2 pieces of paper, adding a couple of extra items towards the end. He discovered there was a phosphorescent substance giving off rays of some sort. On a side note, he discovered the element thorium.
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Marie & her husband Pierre Curie both worked in a shack of a lab, doing extensive experiments with Uranium. Marie discovered the radioactivity of Uranium, & disproved the misconception that atoms are indivisible. She & her husband also discovered 2 new elements: Polonium & Radium.
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Thomson experimented with cathode rays, which led to the discovery that electrons have a negative charge to them. He also discovered isotopes & invented the mass spectrometer, which measures the mass-to-charge ratio of elements.
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Robert Millikan discovers/figures out the charge of electrons. He explained with his equations, the charge of electrons. He used the classic oil drop experiment. Very efficient.
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Niels Bohr proposed a completely new idea for the atomic model in 1913. He looked at Rutherford's model, & with much reasoning & many math equations, disproved Rutherford's theory. Bohr said electrons fly around the nucleus & can change their energy in certain steps.
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Ernest Rutherford made many discoveries with the Gold Foil experiment. He was also the first scientist to transform a nitrogen atom into an oxygen atom. This man showed it is possible to transform atoms into other atoms.
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In 1932, (Sir) James Chadwick discovered the neutron. Interestingly enough, he was experimenting with making ions when he came across this discovery. This was important in leading upto the creation of Uranium 235!
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The Manhattan Project was a huge war project meant to build a war-winning atomic bomb. Perhaps the most important component was uranium-235, a rare isotope of uranium. Despite difficulty, these scientists had to seperate certain parts of the abundant uranium-238 to transform it into the potent isotope required.
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With contributions from 15 - 20 scientists, the Quantum Model tells us we can't know the exact position/momentum of electrons all at once. Since electrons do move fast however, this model uses an electron cloud which predicts where an electron should be.
