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460 BCE
Democritus
All matter made is made small particles with different properties. -
300 BCE
Aristotle
All things made of either earth, fire, water, or air. -
Antoine Lavoisier
Created the Law of Conservation, stating mass cannot be lost or gained. -
John Dalton
All matter is made of atom and all atoms that make up the element have same mass. -
Amedeo Avogadro
Equal volumes of different gases have the same number of molecules. -
Jöns Jacob Berzelius
Made table of atomic weights of 43 elements. Discovered Silicon and Selenium. -
Dmitri Mandeleev
Created first Periodic Table of the Elements. -
J. J. Thomson
Discovered electrons with cathode-ray tube, along with Plum Pudding Model stating that protons were inside nucleus of meterial like plum pudding with electrons surrounding. -
Henry Moseley
Used X-Rays to study atomic structures and found that atomic number equals number of protons in the element. -
Erwin Schrodinger
Said that atom has an "electron cloud", when electrons were likely to be found, but not always in one spot, surrounding the nucleus. -
James Chadwick
Discovered the existence of the neutron in the atom. -
Henri Becquerel
Discovered radioactivity. -
Marie Curie
Discovered radium and polonium and made the word Radioactivity -
Max Planck
Created the Quantum Theory by describing glowing matter using quanta. -
Ernest Rutherford
Did Gold Foil Experiment, proving the existence of the nucleus of an atom. The forming the Rutherford Model. -
Niels Bohr
Formed the Planetary Model, which stated that electrons orbit the nucleus like the moon orbits earth. Also that the Periodic Table can predict atomic structure. -
Robert Millikan
Found the charge of the electron. -
Werner Heisenberg
Created the principle of Indeterminacy, stating that position and velocity of a particle is unknown. -
Lise Meitner
Discovered nuclear fission.