ch7 - Goals Chapter 7 Atomic Structure Describe the...

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Chapter 7 Atomic Structure Goals Describe the properties of electromagnetic radiation. Understand the origin of light from excited atoms and its relationship to atomic structure. Describe experimental evidence for wave- particle duality. Describe the basic ideas of quantum mechanics. Define the quantum numbers ( n , l , and m l ) and their relationship to atomic structure. Electromagnetic Radiation Energy can be transferred between atoms & molecules in the form of light or electromagnetic dual nature of light: wave and particle transverse wave: perpendicular oscillating electric and magnetic fields wavelength, frequency, Amplitude speed, c Electromagnetic Radiation Wavelength, (lambda) : distance traveled by wave in 1 complete oscillation; distance from the top (crest) of one wave to the top of the next wave; or successive troughs/nodes wavelength Visible light wavelength Ultaviolet radiation Amplitude Node All visible & invisible wavelengths are called electromagnetic radiation; wavelength- frequency-color  Electro mag netic Spectrum the entire range of electromagnetic radiation wavelength, , measured in m, cm, nm, Å (angstrom) 1 Å = 1  10 −10 m = 1  10 −8 cm frequency, (nu) , measured in s −1 (hertz) (Hz): number of complete oscillations or cycles passing a point per unit time (s) speed of propagation, c distance traveled by ray per unit time in vacuum; all electromagnetic radiation travel at same rate (speed of light) c = 2.998 x 10 10 cm/s = 2.998 10 8 m/s ( 670 10 6 mph)
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which has a frequency of 4.80 x 10 14 s −1 ? equation: c =    1 14 1 8 s 10 4.80 s m 10 2.998 ν c λ = 6.25 10 −7 m m 10 1 nm 1 ms 10 6.25 9 - -1 7 Mycobacterium tuberculosis can be destroyed with ultraviolet light (255 nm). What is the frequency of this radiation? Planck’s equation Planck studied black body radiation, such as that of a heated body, and realized that to explain the energy spectrum he had to assume that: 1. An object can gain or lose energy by absorbing or emitting radiant energy in QUANTA of specific frequency ( ) 2. light has particle character ( photons ) Planck’s equation is λ c h E h = Planck’s constant = 6.626 10 −34 J s/photon E = energy of one photon Compact disk players use lasers that emit red light with a wavelength of 685 nm. a) What is the energy of one photon of this light? b) What is the energy of one mole of photons of that red light? Plan: , nm   , m a) E, J/photon b) E, J/mol m 10 685 nm 1 m 10 nm 85 6 9 -9 λ c h E mol photons 10 6.022 photon J 10 2.90 E 23 19 E = 2.90 10 −19 J/photon Energy of 1 mole (Avogadro’s amount) The Photoelectric Effect Light can strike the surface of some metals causing electrons to be ejected. It demonstrates the particle nature of light.
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This note was uploaded on 09/08/2010 for the course CHM 2045 taught by Professor Vxv during the Spring '10 term at College of the Canyons.

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ch7 - Goals Chapter 7 Atomic Structure Describe the...

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