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Unformatted text preview: 1 Chapter 6 Electronic Structure of Atoms Waves A wave can be thought as a vibrating disturbance by which energy is transmittedFrequency ( nu): The number of waves passing a given point per unit of time Waves are characterized by their length, height and frequency. 2 2 Waves (cont) Wavelength (Lambda): The distance between corresponding points on adjacent waves.Amplitude: The vertical distance from the midline of a wave to to the peak. Electromagnetic Radiation D e f i n i t i o n : Electromagnetic radiation is the emission and transmission of energy in the form of electromagnetic waves. All electromagnetic radiation travels at the same velocity: the speed of light ( c ). c = 3.00 10 8 m/s. c = wavelength: SI unit: m, cm, nm frequency: SI unit Hz or /s 4 3 c = = c / = = 8.24 m E x a m p l e 1 : What is the wavelength (in meter) ofan electromagnetic wave whose frequency is 3.64x10 7 Hz ? 3.00 x 10 8 m/s 3.64 x 10 7 /s E x a m p l e 2 : The wavelength of the green light from a traffic signal is centered at 522 nm. What is the frequency of this radiation? 1 nm = 1 x 109 m = = The speed of light is c = 3.00 x 10 8 m/s 522 nm = 522 x 109 m = 5.22 x 107 m 5.22 x 107 m 3.00 x 10 8 m/s = 5.75 x 10 14 /s or 5.75 x 10 14 Hz 6 4 The Nature of Energy According to Max Planck, atoms and molecules can emit or absorb energy only in discrete quantities. He gave the name quantum to the smallest quantity of energy that can be absorbed or emitted in the form of electromagnetic radiation. The energy of a single quantum energy E (joule) is: E = h Planck's constant h = 6.626 x 1034 joule.seconds(j.s) The photoelectric effect The photoelectric effect is a phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum of frequency. Albert Einstein suggested that a beam of light is really a stream of particles of light called photons. He deduced that each photons must possess energy E given by E = h 8 5 E x a m p l e : The energy of a photon is 5.87 x 1020 J....
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 Spring '07
 Wyzlouzil
 Electron

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