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John Dalton [1803]
Developed The Atomic Theory1. All matter is made of
particles called atoms2. Atoms of the same
element are identical3. Compounds are made
of 2 or more elements 4. Elements combine in a
fixed ratio to create compounds
JJ Thomson [1897]
▣ Discovered the electron during his cathode ray tube experiment
▣ Model: Plum Pudding Model (or the Chocolate Chip Cookie Dough Model) with a positively-charged cloud of “dough” and negatively-charged interspersed “chips”
Ernest Rutherford [1907]
▣ One of Thomson’s students!▣ Is credited with discovering that
atoms are mostly empty space using a gold foil experiment
▣ Model: Planetary Model
Niels Bohr [1913]
▣ Won Nobel Prize in 1922▣ Determined that
electrons have energy levels by studying light patterns
▣ Electrons can jump from level to level - jumping away from the nucleus requires the electron to absorb energy, falling towards the nucleus will cause the electron to emit energy (light)
Erwin Schrödinger [1926]
▣ Tried to support Bohr’s model with math
▣ Noticed that electrons sometimes acted like waves
▣ BIRTH OF QUANTUM MECHANICS
Other notable events:
▣ The Periodic Table was organized by Dmitri Mendeleev in 1869
▣ Marie Curie studied radioactivity in 1898▣ Louis de Broglie proposed that electrons have a
wave/particle duality in 1923▣ Neutron discovered by James Chadwick in 1932▣ Enrico Fermi created the first man-made
nuclear reactor in 1942