1. In 450 BC, an idea was proposed that everything was made up of four basic elements: Earth, Air, Water, and Fire. They believed anything ever created was created by some of combination of the four basic elements. It was this belief that things make up other things that later led to the idea of atoms.
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2. In 400 BC, a Greek philosopher, Democritus, proposed the idea that matter was made up of tiny, individual particles. He named these particles "atomos" and developed and atomic theory supporting his idea. This theory ultimately failed at the time, but it did later open gateways for the modern model of the atom.
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7. In 1913, Niels Bohr proposed an idea that electrons move in set, circular movements around the nucleus. Also stated that the further an electron orbited around the nucleus, the higher amount of energy it had. So, the electrons had energy levels orbiting the nucleus. This idea of electron's having energy influenced the other models.
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9. In 1926, Erwin Schrodinger used the Bohr model to define the approximate locations of electrons. He did not attempt to find the exact location of electrons but, rather, their pathways. Based off of three principles: Aufbau, Pauli Exclusion, and Hund's Rule. This model has become the modern model of the atom.
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Citations
1.
2. https://the-history-of-the-atom.wikispaces.com/Democritus
3. http://thehistoryoftheatom.weebly.com/john-dalton.html
4. https://2011modelsb.wikispaces.com/Group5
5. http://study.com/academy/lesson/rutherford-model-of-the-atom-definition-diagram-quiz.html
6. https://sites.google.com/site/historyofanatom/james-chadwick
7. http://thehistoryoftheatom.weebly.com/niels-bohr.html
8. http://www.regentsprep.org/regents/physics/phys05/catomodel/cloud.htm
9. http://science.howstuffworks.com/atom9.htm
http://www.abcte.org/files/previews/chemistry/s1_p6.html
1.
2. https://the-history-of-the-atom.wikispaces.com/Democritus
3. http://thehistoryoftheatom.weebly.com/john-dalton.html
4. https://2011modelsb.wikispaces.com/Group5
5. http://study.com/academy/lesson/rutherford-model-of-the-atom-definition-diagram-quiz.html
6. https://sites.google.com/site/historyofanatom/james-chadwick
7. http://thehistoryoftheatom.weebly.com/niels-bohr.html
8. http://www.regentsprep.org/regents/physics/phys05/catomodel/cloud.htm
9. http://science.howstuffworks.com/atom9.htm
http://www.abcte.org/files/previews/chemistry/s1_p6.html