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Chapter 28

Chapter 28. Atomic Physics. Day 1 Learning Goals. Describe the Rutherford Scattering experiment and explain how it provides evidence for the existence of the atomic nucleus Explain qualitatively the origin of emission or absorption spectra of gases. Day 1 Learning Goals.

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Chapter 28

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  1. Chapter 28 Atomic Physics

  2. Day 1Learning Goals • Describe the Rutherford Scattering experiment and explain how it provides evidence for the existence of the atomic nucleus • Explain qualitatively the origin of emission or absorption spectra of gases

  3. Day 1Learning Goals • State the Assumptions and conclusions of the Bohr model for the hydrogen atom. • Understand the concept of energy levels for atoms so you can: • Calculate energy emitted/absorbed • Write an expression for energy levels • Draw a diagram for the energy levels

  4. Early Models of the Atom • Newton’s Model • Tiny, hard, indestructible sphere • Thompson Model (Watermelon) • Rutherford Model • Bohr Model

  5. Thompson Model

  6. Rutherford Model • Rutherford experiment • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf • Two difficulties with Rutherford’s Model • Unable to explain emission/absorption spectrum • Electron’s violate Maxwell’s Theory of E/M

  7. Rutherford Model

  8. Bohr Model

  9. Bohr Model

  10. Atomic Spectra • Emission Spectrum • Electrons are moving between energy levels and emit specific wavelengths of light • Absorption Spectrum • Electrons absorb specific energies of light • Observed as black lines

  11. Atomic Spectra • Atomic Spectra Simulation

  12. Bohr Model

  13. Bohr Theory of Hydrogen • The four Assumptions of the Bohr Theory • Circular orbits under the influence of the Coulomb Force • Only certain orbits are stable • Radiation is emitted when electrons jump from a higher energy level to a lower energy level • The size of the electron orbits is an integral multiple of (h/2p)

  14. Bohr Theory of Hydrogen • Allowed Energies of the Hydrogen Atom • En= - (13.6/n2) eV • Ground state • Ionization energy

  15. Bohr Theory of Hydrogen • http://www.walter-fendt.de/ph11e/bohrh.htm • http://lectureonline.cl.msu.edu/~mmp/kap29/Bohr/app.htm • http://www.control.co.kr/java1/masong/absorb.html

  16. Bohr Theory of Hydrogen • Lyman Series ( Ultraviolet Radiation ) • Balmer Series ( Visible Light ) • Paschen Series ( Infared Radiation )

  17. Bohr Theory of Hydrogen

  18. Bohr Theory of Hydrogen • Correspondence Principle • Quantum mechanics is in agreement with classical physics when the energy differences between the quantized levels are very small

  19. Successes of the Bohr Theory Model of the Atom Explained Atomic Spectra Predicted Rydberg Constant Gave expression for the radius of an atom Predicted the energy levels of the hydrogen atom Modifications to the Bohr Model Elliptical orbits Orbital quantum number Orbital magnetic quantum number Spin magnetic quantum number Modification of the Bohr Model

  20. Atomic Structure • Principle Quantum Number (n) • Orbital Quantum Number ( l ) • Orbital Magnetic Quantum Number ( ml ) • Spin Magnetic Quantum Number ( ms )

  21. Principle Quantum Number (n) • The values of n can range from 1   in integer steps • Symbols used to represent n-values are K,L,M,N,O,P…

  22. Orbital Quantum Number ( l ) • Values of l can range from 0  n – 1 in integer steps • Symbols used to represent l are: s, p, d, f, g, h, . . . • Number of allowed states are n

  23. Orbital Magnetic Quantum Number ( ml) • Values of ml can range from –l to l in integer steps • Number of allowed states are 2l + 1

  24. Spin Magnetic Quantum Number ( ms ) • 2 options • Up • Down

  25. De Broglie Waves • Angular momentum is quantized • mevr = nħ • Stable orbitals are those that contain an integer multiple of the electron’s wavelength

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