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Period: 300 to
History of Atomic Theory
This is about the Atomic Theory, being in the making nearly 3000 years and counting -
360
Democritus' Theory
HIs theory said that atoms exsist in the atmosphere. These are about the atoms that are present in all the forms of existence. He stated that matter could not be split in half to make a smaller substance.He's the first who proposed the existence of an ultimate particle. -
400
Aristotle's Theory
Aristotle beileved in the four elements: Earth, Air, Fire, and Water. No matter how many times it was split, the particle would be a smaller piece of matter. Since he was the tutor of Alexander the Great, his word remained the atomic law for two millenium -
Dalton's Theory
His theory is the base of the modern theory. He stated that atoms of different elements could be distinguished by differences in their weight. He also stated that all atoms make up elements, leading to the disbelief of Aristotle's Theory. HIs model is the most modern and other scientists base their model off of his. -
Thomson's theory
Thomson is the scientist who identified the negatively charged particles and the positivly charged particles. He discovered that there are even smaller particles inside the atom itself, -
Millikan's Theory
Millikan determined the unit charge of the electron with an oil drop experiment. This experiment allowed the calculation of the mass of the electron and the positive atoms. -
Rutherford's Theory
He disovered the positive atom from the gold-foil experiment. He also discovered that positive atoms are located in a small space near the center and that undiscovered atoms are located in the empty spaces, which make up most the atom. -
Bohr's Theory
His theory is like Rutherford's, but applies quantum theory to Rutherford's structure. He stated that electrons travel around the atom in stationary orbits instead of randomly being placed on the inside of the atom, outside the nucleus. -
Chadwick's Modern Theory
In the 1930's, a scientist named James Chadwick discovered another particle in the nucleus of atoms. It had no electircal charge, making it nearly impossible to discover. These were neutrons. The modern atomic model was made of a positive nucleus that is made of both protons and neutrons. The electrons are in energy levels surrounding the nucleus. This made up the modern atom model most people reconize, protons, neutrons, and electrons.
