Atomic History Lesson
Democritus
•Came up with the idea!
•Named them Atoms
•400 BC
•Aristotle said “He’s a quack!!!”
•Took 2000 yrs to be proved right!
Dalton
•Did experiments
•Wrote the first Atomic Theory
Thomson
•Discovered the Negative Electron!
•Called them Corpuscles however
•Plum Pudding or Chocolate Chip Ice Cream
model.
•Cathode Ray Tube Experiment
Cathode Ray Tube Experiment
•A beam of the unknown particles was aimed
down the tube.
•The screen glowed when hit
• The beam could be moved using a positive
charge
•Hence the particles must be Negative… Electrons
Rutherford
•Discovered the Nucleus and the Positive Protons
•Surmised atoms are made of mostly empty space
•Didn’t know about the Neutrons
•Famous Gold Foil Experiment
Gold Foil Experiment
•Particles shot through thin sheet of gold
•Screen glowed when hit
•Most shots went straight through
•A small amount were deflected
•Hence… the atoms must be made of mostly
empty space with a small dense nucleus
Bohr
•Discovered that electrons live in several distinct layers or
levels
•Electrons Orbit
•Electrons can jump between levels with energy being
added/ released
Heisenberg
•Found that Electrons live in fuzzy regions or
“clouds” not distinct orbits
•Improved on Bohr’s findings
•Electron location can not be predicted
Schrodinger
* Same as Heisenberg, worked with
him
James Chadwick
•Discovered the Neutron
•Tough to find due to no charge!
Murray Gell-Mann
* Discovered Quarks
Stanford Linear Accelerator
(SLAC)
Where the first quarks were found… 1968
Fermi Lab
Chicago, IL
CERN
Switzerland
AND
France