Democtritus (circa 450 B.C.)

• Greek philosopher around 400 B.C.

• Student of Leucippius.

• Lived in the age of the Grecian philosophers (Aristotle).

• Proposed the first Atomic Theory.

John Dalton (1766-1844)

• Considered to be the father of modern Atomic Theory

• Combined work of Democritus, Lavoisier, Proust

• Studied the strength of the attractive or repulsive force between charged objects.
• Lived during the American Revolution.

• Proposed Law of Conservation of Matter.
• Also lived during the American Revolution.

• Proposed Law of Constant Composition.
• Also lived during the American Revolution.

• Stated that electricity is made up of particles.
• Constructed Crooks Tube, which led to the development of the Cathode Ray Tube.
• Lived during the American Civil War.

• Discovered the electron.
• Stated that electrons were negatively charged particles that came from the insides of atoms.
• Proposed the Plum-Pudding Model of the atom.
• Also lived during the American Civil War.

• Discovered the nucleus in 1908.
• Proposed Rutherford Model.
• Found that atoms were mostly empty space.
• Performed alpha particle scattering experiments and found that not all particles went straight through the gold foil.
• Found the nucleus to be positively charged.
• Envisioned the atom as having a positively charged nucleus and electrons scattered around the edge.
• Worked with J.J. Thomson and Geiger, who invented the Geiger counter around 1910
• Otto Hahn, who later discovered atomic fission, worked under Rutherford at the Montreal Laboratory in 1905.
  

• Proposed the Planetary Model in 1913 (also called the Bohr Model).
• Worked in conjunction with Rutherford at Manchester from 1912-1919, during most of these years, World War I was taking place (1914-1918).

• Discovered the neutron in 1935, just after America was recovering from the Great Depression.
• Left University of Manchester just before Neils Bohr started there (1913).

• Measured the electron with his oil drop experiment in 1910, just after Henry Ford started production his Model T automobile. It sold for $850.
• Discovered the charge and mass of an electron.

• Made many discoveries concerning the structure of nuclei.
• Born just after World War I started, died just before the end of the Cold War and the reuniting of East and West Germany.