chem001-chapter03-notes

chem001-chapter03-notes - CHEM 001 Lecture Notes, Prof....

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CHEM 001 Lecture Notes, Prof. Wei-Min Dai 16 Chapter 3 Atomic Structure: Images of the Invisible Atoms • Too small to see with an ordinary microscope • Need scanning tunneling microscope to get an image of an atom – Tells nothing about the structure of an atom • The atomic structure has a close connection with electricity Electricity and the Atom • Volta invented the first battery in 1800 • Electric current is supplied by chemical reactions Electrolysis • Splitting of compounds using electricity • Electrolyte conducts electricity • Electrodes – Cathode negatively charged – Anode positively charged • Ions (charged atom or group of atoms) – Cation is positively charged; moves to cathode – Anion is negatively charged; moves to anode Humphry Davy (1778–1829) Michael Faraday (1791–1867)
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CHEM 001 Lecture Notes, Prof. Wei-Min Dai 17 Cathode Ray Tube • Pass current through a tube at low pressure • Used in TV and computer monitors • Cathode rays travel in straight line unless some kind of external field is applied Thomson’s Experiment • Used cathode ray tube to discover negatively charged particles (electrons) By Joseph John Thomson in 1897 Won Nobel Prize in Physics in 1906 in a magnetic field Cathode Rays • Emitted by cathode • Same thing came from different metals • Electrons – Negatively charged – Found their mass-to-charge ratio – Could not determine mass or charge separately Goldstein’s Experiment • Positive ions could flow in the opposite direction – Mass dependent on gas present in the tube By Eugen Goldstein in 1886 gas discharge tube
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CHEM 001 Lecture Notes, Prof. Wei-Min Dai
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chem001-chapter03-notes - CHEM 001 Lecture Notes, Prof....

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