Movement from Basic Atomic Model to the Quantum Mechanical Model(500 B.C.E. - 2000 C.E.)
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400
Democritus (actually 400 B.C.E.)
Born in cerca 460 B.C. Democritus suggested the theory of atoms at around 400 B.C. He believed that everything was made from small particles known as atoms. Of course at this time he had no evidence, but this would still help future scientists to develop a model for the atom. He proposed the idea of the atom and if the idea hadn't existed then a model could not be made, thus making him a valuable member of science. -
476
Roman Empire falls
Science would be lost for many centuries after this -
Joseph Proust
Proust explained the idea of definate proportions; all compounds which are of the same elements are proportional and made of the same components and are equivalent in mass. This would help in understanding atoms and elements and allow future physicists to create models with a better understanding. -
Period: to
Developing the Atom
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American Capital moved from Philadelphia to Washington, D.C.
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John Dalton
The exact date when Dalton discovered the atomic theory is unclear, however it was sometime in 1803 when he published his findings. Without Dalton's atomic theory the structure of the atom wouldnt exist. He insisted that everything was made from atoms and there were many types of atoms (elements). He set the stage for future studies on the atom. -
New York allows all free men to vote (including blacks)
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Panic of 1837
Depression strikes America -
Abraham Lincoln becomes president
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Fort Sumter is attacked
Sparks anger and is one of the events that starts the American Civil War -
Battle of Gettysburg
Important victory for Union troops during American civil war -
Henri Becquerel
Becquerel was able to discover that some elements give off radiation, thus he discovered that some atoms are unstable. Electrons move very fast and are able to shoot off of the atom completely causing it to decompose over time. This new source of information would assist physicists in further understanding the atom enabling them to make more accurate models that could better represent the electron. -
Sir J.J. Thomson
An English physicist who discovered the electrons. Although at first they were called corpuscles they were later deemed as electrons. This set the field for later physicists. This enabled them to study a more accurate model of an atom and allowed them to better understand the atom. He also made the plum pudding model or thomson model which had a jelly-like spherical shape which was positively charged and it had scattered electrons to balance out the charge. -
Max Planck
Planck was the creator of the quantum theory which helped explain subatomic particles (the particles that make up an atom). He also introduced an equation which helped measure the energy being released or absorbed from subatomic particles. This equation would be deemed Planck's constant and would later help Bohr develop an accurate atomic model which would be an improvement of Rutherford's model. -
Period: to
Developing An Atomic Structure
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Period: to
Developing an Atomic Structure
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Wright Brothers take flight
they get their plane into the sky -
Robert Millikan
Sometime in the year 1910 physicist Robert Millikan began an oil experiment in which he would determine both the mass and charge of an electron. By discovering the mass and charge he would help future physicists such as Rutherford. This would help Rutherford realize the mass difference between the electron and proton and would allow Rutherford to make a model in which electrons orbitted the protons. -
Ernest Rutherford
Rutherford was a british physicist who after experimenting with goldfoil and a radioactive substance discovered that the Thomson model was flawed. Rutherford after experimenting in 1910 concluded in 1911 that protons had to be in the center with a much heavier mass than the electrons and that the electrons must be orbitting the proton. This model would be a large stepping stone into making a perfect model -
Niels Bohr
In the year of 1912 Bohr began to question the Rutherford model of the atom and he would begin making his own. In 1913 he would publish his own model which showed that electrons orbited the nucleus in orbitals that were an established distance away. The electrons would change levels only when gaining or losing energy. His model would be for the time more correct than ever before. -
Louis Broglie
Broglie put forth the idea in 1923 that electrons moved in a wave-like pattern and although he had no evidence it was a great step in science. This would later help Erwin Schrondinger develop wave mechanics which would help create an accurate atomic model. -
Erwin Schrodinger
Erwin was a Austrian physicist who was able to create the basics of quantum mechanics. He wrote papers during the early six months of 1926 and was able to create an equation that could explain the probable location of small particles (electrons). This would later allow scientists to create models of the atom with more accuracy; since now they had an idea of how electrons moved and their probable location. -
Werner Heisenberg
Werner created the uncertainty principle which simply stated that the speed at which a subatomic particle moves and its exact position can not be determined exactly. This would help physicists in understanding that an atomic model cannot be perfect considering that accuracy is not going to be perfect. -
Sir James Chadwick
Chadwick was a British physicist who discovered the existence of the neutron. When experimenting with the element beryllium he discovered that it released a substance with a mass close to that of the protons, but it had no charge. This would help in making an improved model of the atom because the models after this point would include neutrons, protons, and electrons. -
Invasion on Poland begins World War II
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Greek Empire Rises to power (actually 478 B.C.E.)
This would lead to the advancement of science and education. -
Aristotle (actually 368 B.C.E.)
It is not possible to know exactly when Aristotle came up with his atomic theory, but it is believed to be around 368 B.C. He stated that there were four elements of water, fire, earth and air and of these elements there were small atoms that made up everything. Aristotle set the foundation for future physicists because he was correct in the fact that small particles do make up all matter. This bit of understanding would later help in understanding the atom and building a model for it.
