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322
Aristotle
A proponent of the continuum. He believed in four elements of air, earth, water and fire. Aristotle felt that regardless of the number of times you cut a form of matter in half, you would always have a smaller piece of that matter. This view held sway for 2000 years primarily because Aristotle was the tutor of Alexander the Great. -
370
Democritus
He founded the atom and said that all atoms are indivisable. -
Johann Becher (1635-1682) and Georg Stahl (1660-1734)
They developed the Phlogiston theory which dominated chemistry between 1670 and 1790. Basically, when something burned, it lost phlogiston to the air. A problem with the theory was that burning of metals resulted in an increase in its mass. This problem was solved by assigning negative mass to phlogiston. -
John Dalton
All of the given atoms of an element are identical. -
J.J. Thompson
Found out that electrons are in a soup of positive charges. -
Ernest Rutherford
He found out that the nucleous has a positive charge. -
Niels Bohr
Found that electrons have a definite orbits -
Ernst Schrodinger
Found out that electrons are particles and waves at the same time. -
Werner Heisenberg
Electrons are in probability zones alled "orbitals", not orbits and the location can't be pippointed. -
Antoine Lavoisier (1743-1794)
He was the first person to make good use of the balance. He was an excellent experimenter. After a visit with Priestly in 1774, he began careful study of the burning process. He proposed the Combustion Theory which was based on sound mass measurements. He named oxygen. He also proposed the Law of Conversation of Mass which represents the beginning of modern chemistry.