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300
Aristotle
Aristotle did not believe in the whole atom theroy because he thought it was nearly impossible for something to move without matter. He did blieve in four elements; fire, air, water, and earth. Each of the four elements the following four properties; hot, cold, dry, and wet.
*year is in B.C. -
440
Democritus
Democritus was the one that sort of developed the idea of the atom. He believed that matter could constantly break. The smallest bit of matter, or matter particles, was called an atom. His belief is completly opposite of Aristotle's. He belived that there were an infinite amount of sizes, shapes, numbers, and types of atoms. -
Antoine Lavoisier
Antoine was the founder of the elements; oxygen and hydrogen and he also discovered the conservation of mass. He also declared sulfur an element and helped establish the list of the first elements. -
John Dalton
Dalton believed that no atom could be seperated, created, or destroyed and that all elements are made up of atoms. He discovered that chemical reactions will always change the atom. He said that atoms of 2 or more elements could combine together and create a compound. He also believed that one type of a certain atom had a different mass, size, and properties than another type of atom. -
Henri Becquerel
Henri investigated in nuclear radiation and was also the founder of radioactivity. He eventually established radiation as a new property. Some elements had the property while other elements did not. -
Max Planck
Planck didnt really change anyting at all he just added his ideas and bleiefs to what was already known about the element, radiaton. -
J.J. Thomson
J.J. Thomson changed the model of the atom by discovering that hydrogen only had 1 electron. He was also the man that discovered electrons and isotopes. -
Marie & Pierre Curie
Marie and Pierre were the leading cause of the discovery of nuclear fission. They had many theories and discoveries of radioactivity and nuclear energy. -
Ernest Rutherford
Ernest discovered the three types of radioactivity; alpha rays, beta rays, and gamma rays. He came to realize that hydrogen is what helped balance out all of the rest of the elements. He is also the one that discovered a proton, which is also the hydrogen nucleus. -
Henry Mosely
Henry Mosely was the one who discovered isotopes of all the different elements. He also improved the periodic table by correcting mistakes and making it the successful table that it is today. -
Nielis Bohr
Bohr discovered electrons orbit around the nucleus in the atom. He also realized that the amount of electrons determines the property that the atom has. His discoveries gave reasoning to why atoms hace different properties. -
Robert Millikan
Millikan was the one to discover and help us better understand the electron inside of the atom. While he was studying them he came to realize that the electron was a negative(1.592e-19 coulumbo). -
Erwin Schrodinger
Schrodinger improved quantum mechanics by questioning Copgnhangen's interpretation. -
Werner Heisenburg
Werner Heisenburg was caused for changing the atomic model, yet agian, because of his belief of nuetrons in the nucleus. -
James Chadwick
James Chadwick helped lead to the discovery of nuclear fission by discovering the neutron in the atom. He eventually ended up proving that neutrons in the nucleus of an atom really do exsist.
