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Plato stated that all matter is composed of particles called atoms.
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Democritus said that everything is made up into tiny bits called atoms. He also discovered that atoms are indestructible and unchangeable.
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Aristotle created a theory about there being elements. Other than that, he didn't really play a big role.
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Robert Boyle, also known as "The father of chemistry", discovered that atoms must exist based on the relationship between pressure and volume of gas.
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The Alchemists developed the theory that all metals are composed of mercury and sulfur. They also discovered that it is possible to change base metal into gold.
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Lavoisier found that total mass of products and reactants in a chemical reaction is always the same. This led to the theory of the law of conservation of mass.
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Dalton was the first scientist to explain the behavior of atoms in terms of measurement and weight. They revealed his law of partial pressures in 1803 which stated that all elements were made of tiny particles called atoms. He created the Solid sphere of "billard ball" model.
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Mendeleev published the periodic table of elements. It arranged the known elements according to their chemical properties and in order of their relative atomic mass.
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Thomson discovered the electron, a negatively charged part of every atom. His experiments with positively charged particles led to the development of the mass spectrometer proposed plum pudding model.
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A pioneer in researching radioactivity, winning nobel prize in physics and in chemistry. The curries discovered radioactivity and studied radiation and radium.
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Einstein was able to fully prove that atoms did exist. He also demonstrated that electrons could leave metal through usage of light.
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Millikan performed an oil drop experiment which measured electric charge. His hypothesis was to specify the size of the electrons charge/allowed he calculate of the mass of the electron and positively charged atoms.
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Rutherford discovered the atomic nucleus and received a nobel prize for study or radioactivity.
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Neils Bohr created the solar system model. He discovered that the atom in the center has electrons orbiting it. Neils Bohr also caught Erwin Schrodingers attention and later on, Schrodingers created the electron cloud model which was basically the same as the solar system model.
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Mosely observed and measured the spectra of 10 elements that occupied consecutive places in the periotic table. He found this by the method of diffraction of x-rays through crystals.
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Heisenberg created a paper called the uncertainty paper which stated no object, no particle, or atom has a definite position, definite trajectory, or definite momentum.
