final chem notes

final chem notes - Chapter Two Atoms, Molecules, Ions...

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Unformatted text preview: Chapter Two Atoms, Molecules, Ions Atoms, Electrons, and Protons J. J. Thomson discovered the electron in the late 1980s o Beam of particles would be produced in an evacuated tube when a high potential voltage was applied to two electrodes o The beam could be deflected by both magnetic and electrical fields applied to the outside of the tube o The direction of deflection indicated that the particles were negatively charged o Because the cathode could be made of many materials, Thomson concluded that all of the tested materials contained electrons o The metal electrodes in their natural state have no charge o Metals must also have positive particles called protons Cathode Ray Tube partial vacuum cathode - Beam of electrons anode + electron beam deflected by electric or magnetic field Rutherford showed that most volume of an atom is empty space o Fired a beam of alpha particles containing 2 positive protons and 2 neutrons at a very thin sheet of gold foil Most of the alpha particles passed through undeflected Some were deflected at a very high scattering angle The high angle scattering could only result from the collision of an alpha particle with an extremely high density of positive charge Showed that all positive protons in the gold atom were concentrated in a very small volume the nucleus The empty space around the nucleus allows the alpha particles to pass undeflected Rutherford scattering experiment proves existence of nucleus Alpha particles (2p + 2n) high angle scattering gold foil low angle scattering Rutherford- when alpha particles are shot at an atom no scattering high angle scattering Robert Millikan measured the charge of an electron o Beam of very small oil droplets allowed to enter a chamber where a beam of x-rays created negatively charged droplets o Droplet allowed to fall through the air where its terminal velocity was measure from the time required to pass two crosshairs...
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This note was uploaded on 02/23/2011 for the course CHEM 1421 taught by Professor Hopkins during the Fall '08 term at LSU.

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final chem notes - Chapter Two Atoms, Molecules, Ions...

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