18 Chapter 2: The Atom An atom is the smallest particle of an
Chapter 28 The Atom
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Transcript of Chapter 28 The Atom
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Chapter 28 The Atom
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Objectives
• 28.1 Explain the structure of the atom • 28.1 Distinguish continuous spectra from a
line spectra • 28.1 Contrast emission and absorption spectra • 28.1 Solve problems using the orbital radius
and energy level equations
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Objectives
• 28.2 Describe the shortcomings of the Bohr model of the atom
• 28.2 Describe the quantum model of the atom • 28.2 Explain how a laser works and describe
properties of laser light
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Different Models of the Atom
• Dalton: Billiard Ball – Indivisable
• J.J. Thomson– Plum Pudding Model
• Rutherford– The Nuclear Model (Positive nucleus with orbiting
electrons)– Others have built on this model
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Some Terms
• Alpha Particle: Helium Particle with a positive charge
• Emission Spectrum: Wavelengths emitted by an atom is called its – Absorption Spectrum: Same idea, but what
wavelengths are absorbed• Spectroscope: Used to determine the
wavelengths of visible light given off
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• Continuous Spectrum produced by having very hot objects– A theoretical black
body produces a continuous spectrum
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• Spectroscopy: Identifying elements by their emission spectrum or absorption spectrum
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Red Shift: Moving Away Blue Shift: Moving Towards
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Rutherford vs Bohr
• Rutherford: Electrons orbit like a planet orbits a star (Planetary model of the atom)
• Issues: Falling into nucleus, radiating all wavelengths
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Bohr Model
• Energy Quantized: Electrons only fall when giving off energy
• Falls and jumps correspond to certain energies
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Terms
• Energy Levels: Refers to the orbital's around the nucleus (Noted as n = 1, n = 2). Also called the Quantum Numbers
• Ground State: When an electron has the lowest energy level allowed
• Excited State: When an electron has absorbed energy and has moved to a higher orbital. Don’t last long (nanoseconds) at the level before falling
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From Last Chapter
• hf (energy emitted) = Eexcited – Eground
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• What wavelength of light is required to make hydrogen’s electron jump from n = 1 to– N = 2– N = 3– N = 4
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Elements beyond Hydrogen
• Require different amounts of ionization energy (Graph shows outside electron)
• Top Right
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Atom Size
• Large = More Lines
• Uranium on Bottom
• Hydrogen on Top
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Molecules verse Atoms
• Would also have a much larger range of emission lines and spectra
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• How many eV’s required for Helium’s 588nm emission? How many eV’s required for Heliums 402nm emission?
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How much energy between shells?
• Follows (1/n2)
• If the n = 1 is equal to – 16 eV, how many eV of energy does a– N = 2 electron have?
• - 16 eV x (1/22) = - 4 eV– N = 4 electron have?
• How much energy is released going from N = 4 to N = 2? What wavelength is that?
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Back to Waves
• Electron Cloud: Represents a high (90%) probability of finding an electron
• Quantum Mechanics: The Study of the properties of matter using its wave properties
• Coherent Light: When waves of light are in sync with one another, maxima and minima lining up
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Lasers
• Create Coherent Light by Stimulated Emission
• An electron in an excited state hit by a photon will fall releasing light in phase with the light that hit it
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Which is coherent?