Quantum - Quantum Theory of the Atom Chapter 7 Introduction...

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Quantum Theory of the Atom Chapter 7
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11/01/11 18:06 Dept/Chem, METU 2 Introduction Elements that exhibit similar chemical properties were placed together in the same column of the periodic table. When metal compounds heated in flame, they emit bright colors. Li(IA) and Sr(IIA): red, Ba(IIA): green The red lights of Li and Sr can be resolved by prism into lines of different colors which distinguishes two elements. How does each atom emit particular color of light? Does the line spectrum tell us the structure ot the atom? We need to understand the arrangement of electrons in an atom (called electronic structure of an atom)
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11/01/11 18:06 Dept/Chem, METU 3 Topics of Discussion The Wave Nature of Light Quantum Effects and Photons The Bohr Theory of Hydrogen Atom Quantum Mechanics Quantum Numbers and Atomic Orbitals
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11/01/11 18:06 Dept/Chem, METU 4 Properties of wave Wavelength, λ , is the distance between any two adjacent point of a wave The frequency, ν , of a wave is the number of wavelengths that pass a fixed point in a unit time, usually second. Unit is Hz (1/s). ν =4 Hz ν =8 Hz λ , wavelength Amplitude time distance
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11/01/11 18:06 Dept/Chem, METU 5 Wave property of light Light is electromagnetic wave. Electric and magnetic fields oscillate synchronously in planes perpendicular to each other. Speed of light in vacuum, c=3x10 8 m/s c= νλ E B
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11/01/11 18:06 Dept/Chem, METU 6 Diffraction of light; wave property Light is diffracted when the refractive index, n, of medium changes. c = νλ (in vacuum) v = c/n (in medium) n air =1 n water =1.5
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11/01/11 18:06 Dept/Chem, METU 7 Electromagnetic Spectrum 1 14 9 8 10 58 . 6 10 1 456 / 10 3 - = s x nm m nm s m x Electromagnetic spectrum covers the range of frequencies and wavelengths of electromagnetic radiation.
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11/01/11 18:06 Dept/Chem, METU 8 Characteristic frequency of Cs atom What is the frequency of one of the spectral lines of Cs with a wave length of 456 nm? 1 14 9 8 10 58 . 6 10 456 10 3 - - = = = s x m x s m x c λ ν
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11/01/11 18:06 Dept/Chem, METU 9 Continuous Spectrum Continuous Spectrum contains light of all colors(wavelengths) Sunlight or light from an incasdescent lamp through the prism
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11/01/11 18:06 Dept/Chem, METU 10 Particle and wave nature of light Atoms in a hot body oscillate with a definite frequency, ν , E = nh ν , n = 1, 2, 3, . . h= 6.63x10 -34 J.s (Plank’s constant) Later, Albert Einstein postulated that light consists of quanta (photon) or particles of electromagnetic energy with energy E = h ν Photoelectric effect, Albert Einstein, 1905 750 0 C 1200 0 C h ν 3h ν 2h ν atom Max Plank (German Physicist) found a formula to explain the blackbody radiation from heated objects.
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11/01/11 18:06 Dept/Chem, METU 11 Photoelectric Effect Photoelectric Effect is the ejection of electrons from the surface of a metal when light shines on it. Results Electrons are ejected, only when ν
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This note was uploaded on 11/01/2011 for the course CHEMICAL E CHEM-107 taught by Professor Bilinmiyor during the Spring '11 term at Middle East Technical University.

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Quantum - Quantum Theory of the Atom Chapter 7 Introduction...

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