Ch07 MSJ jlm - Chapter 7 Electronic Configurations and Electronic the Periodic Table the Robert W Bunsen 1811-1899 Established the science of

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1 Electronic Configurations and Electronic Configurations and the Periodic Table the Periodic Table Chapter 7 Chapter 7 Robert W. Bunsen 1811-1899. Established the science of spectroscopy. Niels H. Bohr 1885-1962.* Related Periodic Table to atomic atomic structure and spectral behavior.
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2 The Wave Nature of Light The Wave Nature of Light Modern atomic theory arose out of studies of the interaction of radiation with matter. Electromagnetic radiation moves through a vacuum with a speed of 2.99792458 × 10 8 m/s. (We will usually round off to 3 x 10 8 m/s) Electromagnetic waves have characteristic wavelengths ( λ29 and frequencies ( ν ) . Example: visible radiation has wavelengths between λ = 400 nm (violet) and 750 nm (red).
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3 The Wave Nature of Light The Wave Nature of Light Some examples of EM radiation: visible light ultraviolet radiation (UV) infrared radiation (IR) radio waves microwaves x-rays ?sound waves?
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4 The Wave Nature of Light The Wave Nature of Light The frequency , ν , of a wave is the number of cycles which pass a point in one second. The speed of a wave, c , is given by its frequency multiplied by its wavelength: c = ν λ where c = 3 x 10 8 m.s -1 (the “speed of light”) The wavelength, λ, is the distance between crests in a wave
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5 Short wavelength High frequency as λ ν Long wavelength Small frequency as λ ν
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6 The Wave Nature of Light The Wave Nature of Light
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7
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8 Quantized Energy and Photons Quantized Energy and Photons Some problems affecting science in 1900 : Blackbody radiation Blackbody radiation Photoelectric effect Photoelectric effect Line spectra Line spectra Spiraling of electrons into nucleus Spiraling of electrons into nucleus
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9 Quantized Energy and Photons Quantized Energy and Photons Planck Planck: energy can only be absorbed or released from atoms in certain amounts called quanta quanta . This energy is proportional to the frequency ,R, of the radiation. The proportionality constant, h, is called Planck ’s constant and is equal to: 6.626 × 10 -34 J.s E = hR Matter can absorb or emit energy only in quantum units which are multiples of hR : ΔE = nhR where n=integer
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10 Quantized Energy and Photons Quantized Energy and Photons The Photoelectric Effect The Photoelectric Effect The photoelectric effect provides evidence for the particle nature of light -- “quantization”. If light shines on the surface of a metal, there is a point at which electrons are ejected from the metal. The electrons will only be ejected once the threshold frequency , υ, is reached. Below the threshold frequency, no electrons are ejected. This is consistent with the Planck statement that light energy depends only on frequency.
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11 Quantized Energy and Photons Quantized Energy and Photons The Photoelectric Effect The Photoelectric Effect
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12 Energy of ejected electrons threshold frequency ν o frequency, ν The Photoelectric Effect The Photoelectric Effect Einstein assumed that light traveled in energy packets called photons .
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This note was uploaded on 04/12/2011 for the course CHEM 1420 taught by Professor Acree during the Spring '08 term at North Texas.

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Ch07 MSJ jlm - Chapter 7 Electronic Configurations and Electronic the Periodic Table the Robert W Bunsen 1811-1899 Established the science of

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