CHAPTER 8_Part I_F2006

CHAPTER 8_Part I_F2006 - CHAPTER 8 ELECTRONS IN ATOMS...

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CHAPTER 8 – ELECTRONS IN ATOMS ATOMIC STRUCTURE AND PERIODICITY WHY ARE CHEMICAL PROPERTIES PERIODIC? Isaac Newton and  classical mechanics . ..  good for baseballs and  planets, not so hot for atoms What we already know . .. atoms = protons and neutrons in the  nucleus; electrons = outside the nucleus The issue now: let's be a bit more precise about what/where the  electrons are Why? THAT'S WHERE THE CHEMISTRY IS! Quantum mechanics  ... incorporation of wave and particle aspects  of matter into a single comprehensive theory The early 20th Century was the Century of the electron. But first, let's talk about waves and ELECTROMAGNETIC  RADIATION  James Clerk Maxwell . .. (1865) . .. light is electromagnetic radiation waves . .. wavelength and frequency    hertz . .. amplitude . .. nodes . .. velocity IMPORTANT: λν = c c = 3.00 x 10 8 m / s
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IMPORTANT: the electromagnetic spectrum, of which visible light is  just a small section EX. National Public Radio locally is on a radio station operating at  90.9 MHz (where MHz = megahertz = 10 6  Hz = 10 6  cycles / s). How  does the wavelength of this radiation compare to the wavelength of  radiation used in microwave ovens in the US that operate at 2.45  GHz (where GHz = gigahertz = 10 9  cycles / s)? More about waves . .. traveling waves vs. stationary (standing) waves IMPORTANT: for standing waves, only certain wavelengths are  possible an example of  QUANTIZATION
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The real question: where do the electrons live? Early work: "On the Emissions of Light from Gas Discharge Tubes" aka. Atomic Spectra OBS.: white light and the continuous spectrum OBS.: gas discharge tubes and line spectra . .. emission spectra
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OBS: every element has a different line spectrum OBS: Absorption spectra
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OBS. Absorption spectra vs. Emission Spectra RESULT: the Rydberg equation fit experimentally observed data (ie. wavelengths in the emission  spectrum of hydrogen) to some mathematical relationship
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1 /  λ   = R ( 1/2 2  - 1/ n 2
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This note was uploaded on 02/27/2008 for the course CHEM 025 taught by Professor X during the Fall '06 term at Lehigh University .

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CHAPTER 8_Part I_F2006 - CHAPTER 8 ELECTRONS IN ATOMS...

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