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200
440 BC - Democritus
Democritus's theory said that if you cut something in half over and over again that it would eventually get to the stage where you cannot cut it anymore. Democritus named this particle a atom which comes from the Greek word atomos, meaning "not able to divide." -
201
382 BC - Aristotle
he did not believe Democritus's theory and thought that the particles could still be divided. Since he had a strong influenc on people most people believed him. -
Dalton's Theory
Dalton constructed a theory that explained why atoms formed certain ratios to form compounds. His reason for that was because the compounds were made of single atoms. -
Thomson
Thomson reviewed the theory of and earlier scientist and found mistakes in the theory. he discovered that there are smaller particles inside atoms. This meandt that atoms could be split into smaller particles. He carried out this experiment with a cathode-ray tube. While conducting the experiment he noticed that the beam was attracted to a positively charged plate. His canclusion was that the particles were negatively charged because they were attracted to the plate. -
Rutherford
He was the first one to relize that atoms were soft particles. When he conducted an experiment. During the experiment he thought all the partiles would go through the foil but instead they bouced off of it or back. -
Rutherford
In 1911 he made a model of the atom that consisted of the nucelus being very small and dense, and positively charged. the atom's nucleus is proposed to be 100,000 times smaller than a gold atom. -
Bohr
He created a model of the atom where the electrons follow certain paths and have energy levels in which they can jump to and from them. -
Schrodinger and Heisenberg
They suggested that electrons are found in a certain region and have unpredictable paths which disagreed with Bohr's theory. The region where elcetrons can be found is called a electron cloud.
