Chem222-Lecture #1 ppt.

Chem222-Lecture #1 ppt. - Basic Principles A)Electrostatic...

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Basic Principles A)Electrostatic charges of the same sign repel each other. 1)VSEPR Theory – Sets of electrons will always arrange themselves to maximize the distance between the sets. 2) Electrons will always distribute themselves in such away as to minimize the electron density. 3) Substances which are positively charged will distribute electrons in such away as to delocalize the positive charge. B) Electrons have both particle and wave like properties. 1) No two electrons can occupy the same space at the same time. (particle property) 2) Electrons in an atom or molecule are best described by a wave equation (periodic function)
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Properties of Periodic Functions 1)Vibrating string (EXAMPLE) A) Note: varying the length of the string changes the wave length. (boundary condition = the ends of the string are fixed ) B) Are there any other vibrations possible where the ends of the string are fixed ? (Answer = yes) The simplest vibration is called the fundamental and all The other possible vibrations are called overtones.
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C) The fundamental and overtone vibrations do not interfere with each other. (Mathematically we say the vibrations are orthogonal to each other.) D) The points on the string that do not move, other than the ends are called nodal points. 2) Vibrations in 2-dimensional space. ( Drum Surface ) Shown below are some of the allowed vibrations Of the surface of a drum. A) Note : nodal points are now nodal lines. B) There are 2 first overtones, 3 second overtones etc. .
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3) Vibrations in 3- dimensional space ( sponge rubber ball glued to the inside of a steel sphere) ( see applet : falstad.com/mathphysics.html) A) Note: Nodes are now surfaces. B) The number of first overtones is now four. C) See if you can hazard a guess of what some of the second overtones will look like .
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Hydrogen Atom 1)Consists of a proton in the nucleus and an electron spherically distributed with respect to the proton. A) We will describe the electron with a periodic function ( wave equation ) called ψ. B) ψ will have the following properties. I) The value of ψ asymptotically approaches zero at infinity. (boundary condition) II) The value of the sum over all space with respect to the nucleus of ψ 2 = 1. (normalization) ( ψ 2 is a measure of the probability of finding the electron at a particular point in space at a particular time. )
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2) The electron in any of these vibrational states is attracted to the nucleus. A) In order to separate the electron from the nucleus
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This note was uploaded on 02/20/2011 for the course CHEM 222 taught by Professor Harding during the Spring '08 term at CUNY Hunter.

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Chem222-Lecture #1 ppt. - Basic Principles A)Electrostatic...

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