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Notes6 Material Type: Notes; Professor: Kidwell; Class: GENERAL CHEMISTRY I; Subject: Chemistry; University: Harper College; Term: Spring 2015;
Typology: Study notes
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In 1808 , Dalton presented his theory of atoms: Paraphrasing:
Avogadro’s Hypothesis led to the following relation: If; 2 volumes of hydrogen + 1 volume of oxygen → 2 volumes of water
Then; 2 molecules of hydrogen + 1 molecule of oxygen → 2 molecules of water
Based on all of this work the idea of “the atom” was clearly a good one. So the next logical step should be to ask: What is an atom?
He then used this beam in an applied magnetic field to determine the charge-to-mass ratio of an electron
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He reasoned since all metal electrodes produced “ cathode rays ” that all elements must contain electrons Also, that there must also be positive charges present and that the electrons are randomly embedded in the “ positive cloud ” This is called the “ Plum pudding ” model of the atom The next major advancement in understanding came when Robert Millikan
This allowed him to determine the magnitude of the e
charge combined with the charge-to-mass ratio of the electron by Thomson allowed him to calculate the mass of an electron
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First recognized in 1896 by Henri Becquerel He followed this observation to discover three types:
charge (7300 times the e
mass) Now we know it as a He nucleus