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400
Democritus
Democritus theorizes that everything in the universe is composed of tiny particles named atoms -
Law of Conservation of Mass
States that mass is neither created nor destroyed -
Antione Lavoiser
Discovered oxygen molecule and came up with Law of Constant Composition -
Law of Definite Proportion
Proust stated that a chemical compound has the same amount proportions of elements -
Joseph Luis Proust
Published the law of definite proportion and this helped Dalton to propose his atomic theory -
Dlatons Atomic Theory
Provided explanations for concepts and ideas -
Dmitri Mendeleev
Made first periodic table based on atomic mass -
Eugen Goldstein
Discovered atoms have positive charges -
J.J. Thompson
Creates Plum Pudding Model and discovers electron -
Cathode Ray Tube
Used to find charge to mass ratio of an atom -
Plum Pudding Model
Considered that the inside of an atom was like raisin bread -
Marie Curie
Dicovered atoms were divisible -
Robert Millikan
Discovered unit of charge in an electron, positively charged atoms and the mass of an electron -
Gold Foil Experiment
Used by Ernest Rutherford to figure out what nucleus really looked like and disproved Plum Pudding Model -
Rutherford Model
Better model of atom because people had the components but didnt know how they fit -
Ernest Rutherford
Discovered that atons have central positive nucleus surrounded by negative electrons -
Bohr Planetary Model
Explain structure and actions of complex atoms -
Niels Bohr
Led to possible calculation of energy level and that light emission is from electrons moving in lower level -
Henry Moseley
Rearranged periodic table based on atomic number not atomic mass and new periodic table was better and allowed for progression of atoms -
Erwin Schrodinger
Learned how to find probability of where an electron is located in an orbital -
Quantum Mechanical Model
Explains the behavior of atoms in the atomic and subatomic realms -
James Chadwick
Discovered nuetron and led to discovery of fission and atom bomb -
LIse Meitner
Explained nuclear fission and modeled the nucleus