Period: 350 to
Contributions to the Field of Chemistry
Democritus - 460 B.CLink
Developed the idea of atoms in a void.
Developed the idea of "Corpuscles" that were subject to attractive and repulsive forces.
Proposed a modern atomic model based on experimentation not on pure reason.
Discovered that X-rays excite fluorescence in certain substances
Neils BohrLink-Formulated the ‘complementarity principle’
-Made major contributions to the work on radioactivity that led to the discovery and exploitation of nuclear fission
-created the liquid-drop model of the nucleus
Discovered Electrons and created the Raisin Pudding Model
Marie and Pierre Curie (1867 & 1856)Link
They established that the heavy element thorium was radioactive and discovered two new elements: polonium and radium. They refined techniques for extracting radium from ores.
Shot alpha (α) particles at gold foil and discovered that a “nucleus” is positive & holds most of an atom’s mass.
James ChadwickLinkProved that neutrons, neutral particles in the nucleus that made up approximately half the mass of an atom, did exist