SABIC CHEM 101 Chapter 2 - Part 2

SABIC CHEM 101 Chapter 2 - Part 2 -...

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Atomic Structure – Early Experiments Scientists became interested in the structure of the atom – that is, what is the atom composed of and how is it held together. Postulated the existence of electrons using cathode‐ray tubes . Determined the charge‐to‐mass ra9o of an electron. The atom must also contain posi9ve par9cles that balance exactly the nega9ve charge carried by par9cles that we now call electrons. J. J. Thomson (1898—1903)
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Thomson’s Experiment Applying high voltages to a cathode-ray tube resulted in a ray produced at the positive electrode that travelled to negative electrode. http://www.youtube.com/watch#!v=O9Goyscbazk&feature=related
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Thomson’s Experiment Conclusion 1: The ray was a stream of negatively charged particles (electrons) Conclusion 2: All atoms must contain electrons Conclusion 3: The charge-to-mass ratio of an electron is -1.76 x 10 8 C/g Thomson proposed a structure of an atom as a spherical cloud of positive charge with the negatively charged electrons are suspended – The Plum Pudding Model
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Atomic Structure – Early Experiments Performed experiments involving charged oil drops . Determined the magnitude of the charge on a single electron. Calculated the mass of the electron. Robert Millikan (1909)
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Millikan’s Experiment http://www.youtube.com/watch?v=XMfYHag7Liw
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Millikan’s Experiment Conclusion 1: The charge on an electron is 1.602176487(40) × 10 19 C Conclusion 2: The mass of the electron is 9.11 × 10 19 kg
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This note was uploaded on 10/13/2011 for the course CHEM 101 taught by Professor Fitts during the Fall '08 term at UPenn.

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SABIC CHEM 101 Chapter 2 - Part 2 -...

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