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500 BCE
The Alchemists
develop the theory that all metals are composed of mercury and sulfur and that it is possible to turn metal to gold -
370 BCE
Democritus
atoms are unbreakable into smaller parts, there is empty space between atoms -
332 BCE
Aristotle
He believed all matter was made up of individual particles. Believed there were 4 elements earth, fire, water, and air. -
427
Plato
elements had the following shape(fire) tetrahedron (air) octahedron (water) icosahedron(earth) (cube) -
Robert Boyle
Boyle mainly studied gases .
He also was able to tell the difference between a mixture and a compound . -
Lavoisier
he came up with theory of elements. Elements are individual particles that can not be separated. -
John Dalton
- All elements are composed of atoms that are indivisible
- All atoms of the same element are identical
- Atoms of different are different they always have different numbers of protons and they may also differ in mass numbers
- Atoms of different Elements can combine with each other in simple whole number ratios to form compounds .
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Dmitri Mendeleev
He created the first periodic table Elements arranged by increasing weight . -
J.J.Thompson
He discovered the electron. -
The curies
French physicists Pierre and Marie curie discovered the strongly radioactive elements polonium and radium which occur naturally in uranium minerals -
Albert Einstein
Proved there are atoms. -
Robert Millikan
determined the change of the electron using the ''oil - drop method" -
Ernest Rutherford
The gold foil Experiment He demonstrated that the atom has a small and dense nucleus -
Neils Bohr
He said electrons move only in certain orbits and that is why they emit light. Solar System Model of the Atom -
Henry G. J. Mosley
Mosely's Law says that is a relationship between wavelength and atomic number -
Werner Heisenberg
discovering the uncertainty principle , you don't know exactly where an electron is
