Chapter 7 Lecture

Chapter 7 Lecture - Chapter 7 Electron Structure of the...

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Electron Structure of the Atom Chapter 7
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Questions for consideration 1. What is light and how can we describe it? 2. How can we describe the behavior of the electron in a hydrogen atom? 3. How can we describe electrons in all atoms? 4. How does the arrangement of electrons in atoms relate to the arrangement of elements in the periodic table? 5. Which electrons are chemically important in an atom? 6. How does the electron arrangement in ions differ from that in atoms? 7. What properties of atoms are related to their electron arrangements?
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Math tools used 1. Units and conversions
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The Wave Nature of Light
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Frequency and Wavelength c = l n C = 3.00 x 10 8 m/s
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Amplitude (intensity) of a wave.
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Regions of the electromagnetic spectrum.
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Different behaviors of waves and particles.
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The diffraction pattern caused by light passing through two adjacent slits.
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The Particle Nature of Light
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Blackbody radiation D E = D n h n D E = h n when n = 1 light bulb filament 2000 K n = quantum number (1,2,3…. .) h = Planck’s constant (6.626 x 10 -34 J*s) n = frequency 1) Hot glowing object can emit or absorb only certain quantities of energy. 2) Hot object’s radiation is emitted by the atoms contained within it. 3) Atom can only have certain quantities of energy 4) A change in the atom’s energy results from the gain or loss of 1 or more (quantum or quanta) of energy
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Photoelectric effect – flow of current when monochromatic light of sufficient frequency shines on a plate .
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The photoelectric effect 1) Presence of a threshold frequency a. Wave theory – associates energy of light with intensity not frequency (color) b. Photon theory – energy depends on frequency (h n ) so it predicts a threshold frequency 2) Absence of a time lag a. Wave theory – in dim light there would be a time lag before current flowed (electrons have to absorb enough energy to break free) b. Photon theory – electron breaks free the moment it absorbs one photon of enough energy.
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Take home message You have to accept that light behaves both as a particle and a wave.
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The line spectra of several elements.
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Flame test animation
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Ground and Excited States • Electrons “prefer” to be in the lowest energy level – levels closest to the nucleus – Ground state • Excited state – electron goes from the lowest energy level to a higher energy level
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Bohr’s Explanation • Light can have only discrete amounts of energy – Energy is quantized • Electron can have only these values and no others
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Emission spectrum animation
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What is the photon energy of the light that produces the red line in the hydrogen spectrum? Of the four lines in the hydrogen line spectrum, which
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Chapter 7 Lecture - Chapter 7 Electron Structure of the...

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