Ch 11 Packet - Chapter 11: Atomic Theory: The Quantum Model...

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CHEM 139 Chapter 11 page 1 of 15 Chapter 11: Atomic Theory: The Quantum Model of the Atom Problems: 1-21 (odd only), 31-57 (odd only), 61, 63, 67, 79 11.1 LIGHT … Also Known As Electromagnetic Radiation All objects at temperatures above absolute zero emit light at all times “radiant energy” Light travels through space as a wave. While light may appear to travel instantaneously, it actually travels at a finite speed, 2.998 10 8 m/s (about 186,000 miles per hour). This is called the speed of light (symbol c ). Waves have the both a wavelength and a frequency : wavelength ( = Greek “ lambda ): distance between successive peaks frequency ( = Greek nu ): number of waves passing a given point in 1 s
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CHEM 139 Chapter 11 page 2 of 15 Electromagnetic Spectrum: continuum of radiant energy (see Fig. 11.1 on p. 304) There are many forms of light: X-rays, radio waves, microwaves, etc. They are ONLY different in terms of wavelength/frequency. visible region: the portion of the EM spectrum that we can perceive as color For example, a "red-hot" or "white-hot" iron bar freshly removed from a high-temperature source has forms of energy in different parts of the EM spectrum red or white glow = radiation within the visible region warmth = radiation within the infrared region How is energy related to wavelength and frequency? As wavelength , the frequency , and the energy As wavelength , the frequency , and the energy Classical Descriptions of Matter James Maxwell (1873) visible light consists of electromagnetic waves John Dalton (1803) Atoms are hard, indivisible, billiard-like particles; all atoms are the same Atoms have distinct masses (what distinguishes on type of atom from another). JJ Thomson (1890s) discovered charge-to-mass ratio atoms are divisible because the electrons are one part of atom Ernest Rutherford (1910) shot positively charged discovery of the atomic nucleus (1910)
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page 3 of 15 Transition between Classical and Quantum Theory Max Planck (1900) ; Blackbody Radiation He heated solids to red or white heat Noted matter did not emit energy in continuous bursts, but in whole-number multiples of certain well-defined quantities matter absorbs/emits energy in bundles = "quanta" (single bundle of energy= "quantum") Albert Einstein (1905) ; Photoelectric Effect Photoelectric Effect: Light shining on a clean metal emits electrons only when the light has a minimum threshold frequency, For    no electrons are emitted For    electrons are emitted, more e emitted with greater intensity of light, Einstein applied Planck's quantum theory to light light exists as a stream of "particles" called photons Emission Spectra: continuous or line spectra of radiation emitted by substances a heated solid (e.g. the filament in an incandescent light bulb) emits light that spreads out to give a continuous spectrum = spectrum of all wavelengths of light, like a rainbow
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Ch 11 Packet - Chapter 11: Atomic Theory: The Quantum Model...

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