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2013-01-15 01:34:56
acs chem hist

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  1. democritus
    • 400bc
    • world made of tiny INDIVISABLE particles called atomos.
    • not experimental
  2. dalton
    • early 1800s
    • each element composed of small particles called atoms
    • all atoms of a given element are identical to one another in mass and properties
    • atoms not changed durring reactions (not created or destroyed)
    • compounds formed when more than one element combine; compunds always have same relative number and kinds of atoms
  3. law of constant composition
    • dalton
    • relative number and kinds of atoms constant in compound
  4. law of conservation of mass or matter
    • dalton
    • atoms neither created nor destroyed
    • mass before=mass after reaction
  5. law of multiple proportions
    • two elements can combine in different proportions but they mae different compounds
    • dalton
  6. fundamental principal in chem
    particles with same charge repel, opposite attract
  7. jj thompson
    • late 1800s
    • discovered electrons aka smaller than atom things
    • didn't see them but caused cathodes to flouresce
    • how tv work
    • also calculated charge to mass ratio
  8. robert millikan
    • 1909
    • measured electron charge by seeing that data was multiples of the charge
    • oil drop experiment
    • could determine mass with thompson's calculations
  9. marie curie
    • discovered radioactivity
    • spontaneous emmision of radioactive isotopes
  10. ernest rutherford
    • discovered alpha, beta, gama rays because of diff response to electric field
    • disproved jj thompson's plumb puding model
    • determined that nucleus was small, dense, positive, atom 10000 larger than nucleus
  11. gold foil experiment
    • rutherford
    • passed alpha particles through gold sheet
    • most went through, some deflected
    • discovered protons
  12. discovered neutrons
    james chadwick