09.03 - A Brief History Dalton - compounds (molecules)...

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1 A Brief History Dalton -- compounds (molecules) contain whole #’s of atoms Avogadro -- equal volumes of gas = equal # of molecules Gay-Lussac -- 2 vol “hydrogen” + 1 vol “oxygen” --> 2 vol “water” (all gases), and 1 vol “hydrogen” + 1 vol “chlorine” --> 2 vol “hydrogen chloride” Atomic Masses “hydrogen” = H 2 , “oxygen” = O 2 etc…. Cannizzaro -- If mass of 1 L of H 2 ~ 2, then mass of 1 L of O 2 ~ 32 mass of 1 L of H 2 O ~ 18, etc. . Can derive atomic masses But what if “hydrogen” is H 4 , not H 2 ? So, What’s an Atom? Frankly, just a name for an irreducible chemical species J.J. Thompson -- the electron Mulliken -- got its mass (static electricity) Rutherford -- shot α particles at gold foil Big, positive charge surrounded by small, negative charges Can you characterize atomic composition? How?
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2 Seeing Atoms -- the Scanning Tunneling Microscope Pt and Ni alloy Bright = Ni, Dark = Pt Few nm per side Chains of atoms!! http://www.
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09.03 - A Brief History Dalton - compounds (molecules)...

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