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Jan 1, 1000
Democritis, Greece 400 BC
believed that all matter was made up of atoms. He called it the smallest invisible thing in the universe. What he gave to us was the thought that it could not be seperated. Ultimately, Democritis' model of the atom was a solid spherical mass. He influenced many scientists, but not directly through teaching. -
Jan 1, 1000
Aristotle, Greece 350 BC
Provided scientists with the method of gathering and analyzing information. Even though he believed that the atom could not possibly exist he gave scientists the tools to eventually prove him wrong. Aristotle affected many scientists to come after him as they used his reasoning. -
Period: Jan 1, 1000 to
History of the Atom
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Antoine Lavoisier
Provided us with the conservation of mass theory in chemical reactions. He also defined the difference between the element and the compound allowing scientists to break up natural things that they found. He created the model in which particles revolved around a nucleus, this was called the solar sytem theory at the time. -
John Dalton
He formed the atomic theory. He majorly reinforced the idea that matter was composed of tons of tiny, indevisable particle called atoms. But he added that all atoms had the same atomic weight. According to his work the atom was given the electron balance between the nucleus and the electron cloud. -
Henri Becquerel
When he began to look at uranium he discovered radioactivity in unstable atoms. He than began to identify other radioactive substances.he opened up the idea of a diffent number of electrons in an atom and may have lead to rutherford's model. He was probably in someway connected to the Curies. -
The Curies
The Curies discovered several more radioactive substances such as Radium and Polonium. this strengthened the thought that elements had a balnce to them that could be changed in different ways. they probably were related to Becquerel in some way but it is indecernable. -
J.J. Thomson
Came up with the idea of electrons as he study electrical charge in nature. Was the first to venture into sub-atomic particles came up with the plum pudding model of the atom. This enhanced the previous model by suggesting a random arrangement of elctrons in a matter known as the atom. He taught Ernest Rutherford all about these discorveries. -
Max Planck
Max Planck is known most for developing the Quantum theory in which he said that enrgy was not transfered among atoms in continuos waves but in packets called Quanta. This allowed einstein to come with his theories. This affected the atom in a way which the atom could be seen as reserving energy and then letting it of in sporadic bursts that were seen as color to the human eye. -
Robert Millikan
Robert Millikan is famous for his discovery of the charge of an electron. His research, inspired by Planck, encouraged him to find what the exact charge of an electron was so that the quantum theory could be put into perspective. He did not affect the model but did affect the way the atom was considered in giving off energy. He has no connections with other scientists. -
Ernest Rutherford
Ernest Rutherford was a major changer of the atom. While the atom had earlier been thought to have it's mass spread evenly throughout it, he proved that the weight was in fact in a densely packed core, the nucleus. He suggested that this core was the heaviest part of the atom and that electrons were then spread around it. His model was a large core surrounde by a cloud of electrons. -
Niels Bohr
Bohr was the first to propose that electrons moved in large orbits which circled around the atom's nucleus. He also said that energy from the atom was produced when the electrons jumped from one level to the next in a quick succession. His model looked more like the modern model which has a nucleus surrounded by several rings which the electrons jump back and forth across. -
Henry Mosely
Mosely's work was in discovering that the number of protons should determine where something goes on the periodic table. He created the modern periodic table and showed all of the properties of that time lined up in periods and columns according to atomic number. He was a student of rutherfords and solidified the theory of the # of protons staying the same in an atom, no matter whether original or isotope. He was a student of Rutherford's. -
Erwin Schrodinger
Made the Schrodinger equation which determined the power of energy waves and the probability that the waves govern the movement of electrons. He used this to try and determine the positions of the electrons in the electron cloud. His vew of the atom was like rutherfords, not changing much but just adding to the idea. -
Werner Heisenberg
Werner Heisenberg is most known for developing his uncertainty theory. This states that the more you know about the velocity of an electron the less you know about the momentum and vice versa. This explained that you could never know the exact location of an electron but you could guess within a 90% chance of being right that it would be in a certain region of the electron cloud. This refined the model of the atom by placing electrons in a "cloud', reching all the way back to the plum pudding. -
James Chadwick
James Chadwick was known for discovering the neutrality of the neutrally charged neutron. His teacher, one Ernest Rutherford, had challengd that only charged particles existed. His student then(Chadwick) noticed that mysterious particle was not affected by elctricity and magnetic fields and made the nucleus heavier. This he surmised had a neutral charge and when he identified it he called it the neutron. This changed his model to appear with 2 particles in the nucleus.
