Chy102-Lecture 05 - General Chemistry Chem102 for...

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Unformatted text preview: General Chemistry Chem102 for Engineering Dr. Raafat Aly 5 th lecture 28/11/2007 D o n e 2 Objectives Define the wave and particle nature of light. Mention some important quantum theories. Identify the different quantum numbers. What is Paulis exclusion principle? Illustrate the atomic orbitals, their shapes and sizes. Derive the electronic configuration of elements and ions. 3 Light travels through space as a wave, Waves have many characteristics the most important of which are: a. Wavelength ( , lambda): which is the distance between two consecutive peaks or troughs, most often measured in meters or nanometers (1 nm = 10-9 m) . a. Frequency ( , nu): which is the number of waves (cycles) that pass a given point in unit time. The frequency unit is cycles per second, s-1 or hertz (Hz) The speed at which a wave move through space can be found by multiplying the length of a wave cycle ( ) by the number of cycles passing a point in a unit time ( ) For light, = c = c / Electromagnetic radiation 1. The wave nature of light 4 Today, light is considered to be generated as a stream of particles (quantum of light) called photons. The energy of each photon E, in joule, is given by the equation: Notice from this relation that energy is inversely related to wavelength . J.s 10 6.626 h , t tan Cons s ' Planck c h h E 34- = = = Since all types of electromagnetic radiation travel at the speed of light, short-wavelength radiation must have a high frequency 2. The particle nature of light c is constant 5 Classification of electromagnetic radiation In conclusion, electromagnetic radiation which was previously thought to exhibit wave properties, seems to show some characteristics of particles as well. This phenomenon is referred to as the dual nature of light . Now, Is the opposite is true? That is, does electron, that are normally assumed to be a particle , exhibit wave properties i.e., have wave-like motion? 6 de Broglie wavelength Matter behaves as though it moves in a wave. The wavelength of any particle (electron) of mass m moving at speed v is: v m h = Note that an electron wavelength is inversely proportional to its velocity....
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Chy102-Lecture 05 - General Chemistry Chem102 for...

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