Lesson Plans

Physics 1st Edition ©2002

by James S. Walker

Week 29

Chapter 31: Atomic Physics

College Board Performance Objectives:

• Demonstrate an understanding of the Plum Pudding Model and the Rutherford model of the atom.
• Discuss the Rutherford, Geiger, and Marsden scattering experiment.
• Demonstrate with appropriate diagrams an understanding of emission spectra.
• Sketch diagrams for the Lyman, Balmer, Paschen, Brackett, and Pfund Series.
• Write Bohr's First Postulate and use it to verify standing de Broglie waves.
• Write and illustrate the meaning of Bohr's Second Postulate.
• Calculate the energy emitted per photon per Bohr orbit quantum jump.
• Discuss the quantum mechanical nature of the hydrogen atom.
• Discuss the role of quantum numbers in atomic structure.
• Predict the structure of various atoms.
• Discuss the production of continuous and characteristic X-rays.
• Calculate voltages required to produce X-rays in an X-ray tube.

College Board Lab Objectives:

• Determine the average spacing between the lines of a diffraction grating by using known wavelengths.
• Measure the wavelengths of the visible spectrum of helium.

Suggested Labs:

• Diffraction Grating Measurement of the Wavelength of Light

Resources:

• Student Edition — pp. 1010–1044
• Student Study Guide — pp. 518–532
• Instructor's Solution Manual Volume 2 — pp. 227–242
• Instructor's Solution Manual CD — Chapter 31.doc
• Instructor's Resource Guide — pp. 250–251
• Test Items File — pp. 393–401
• Media Portfolio CD — Lecture Resources Chapter 31

Pacing Guide:

• Early Models of the Atom—day 1
• The Spectrum of Atomic Hydrogen—days 1 and 2
• Bohr's Model of the Hydrogen Atom—days 2 and 3
• De Broglie Waves and the Bohr Model—day 3
• The Quantum Mechanical Hydrogen Atom—day 3
• Multielectron Atoms and the Periodic Table—days 3 and 4
• Atomic Radiation—days 3 and 4
• Lab—day 5
• Block Scheduling
  Early Models of the Atom and The Spectrum of Atomic Hydrogen require one block. Bohr's Model of the Hydrogen Atom and De Broglie Waves and the Bohr Model require a second block. The Quantum Mechanical Hydrogen Atom, Multielectron Atoms and the Periodic Table, and Atomic Radiation require the remaining time.

Key Words:

Critical Thinking Questions:

1. Show that a joule second, Js, is a unit of angular momentum.
2. An electron is in the n = 1 orbit of the Bohr atom which has a radius of 0.5 Å. What is the tangential speed of this electron?
3. A photon with a wavelength of 97 nm strikes a ground state electron in the Bohr hydrogen atom. (a) What is the highest energy state the electron can reach? (b) How many transitions can be achieved from this energy state?
4. Use the Bohr Theory of the Hydrogen Atom and show that |E_n| = nhf_n.
5. A photon of light, , collides with an electron in a Bohr hydrogen atom. (a) What is the energy of this photon in both J and eV. (b) Can this photon raise the n = 1 electron to an excited state? Give a mathematical explanation of your answer.
6. Solve problem 26 on p. 1045 in the textbook.
7. Solve problem 64 on p. 1046 in the textbook.

Answers: 1. proof; 2. 2.0x10⁶ m/s; 3. (a) n = 4 and (b) 6; 4. proof; 5. (a) 4.42x10^–19 J and 2.76 eV, (b) proof; 6. (a) , (b) , (c) for very large n, the frequency of the emitted photon is the same as the electron's orbital motion; 7. 0.0586 nm

Troubleshooting Tips/Error Traps:

• The main result of the Bohr Theory of the Hydrogen Atom is that the energy of the orbiting electron is quantized.
• The student needs to understand that the energy of a photon emitted from a hydrogen atom is equal to the difference of the energies of the initial energy level and the final energy level.

End of Chapter Activity:

1. The Balmer equation is a relationship giving the
   1. change in wavelength of photons scattered by electrons.
   2. kinetic energy of photo electrons.
   3. radii of orbits in the hydrogen atom.
   4. kinetic energy of photoelectrons in terms of frequency of incident light.
   5. frequencies of the lines in the visible spectrum of hydrogen.
2. Geiger and Marsden's scattering experiments showed
   1. the wave nature of matter.
   2. the particle nature of light.
   3. electrons can be diffracted.
   4. the atom has a small positive core.
   5. that photons behave like particles.
3. Bohr's model of the atom assumed that
   1. electrons moved in circular orbits about a positive core.
   2. electrons were concentrated in the core of the atom.
   3. electrons and positive charge were evenly distributed throughout the atom.
   4. electrons and protons were concentrated in the core of the atom.
   5. nuclear force holds the electrons about the nucleus.
4. The Bohr model of the atom is also known as the
   1. plum pudding model.
   2. planetary model.
   3. raisin muffin model.
   4. de Broglie wave model.
   5. blackbody model.
5. In the Bohr hydrogen atom, the quantum jump from the n = 6 to n = 2 energy level results in the emission of a photon in what part of the electromagnetic spectrum?
   1. X-ray
   2. ultraviolet
   3. visible
   4. infrared
   5. microwave
6. In the Bohr hydrogen atom, the quantum jump from the n = 4 to n = 2 energy level results in the emission of a photon in what part of the electromagnetic spectrum?
   1. X-ray
   2. ultraviolet
   3. visible
   4. infrared
   5. microwave
7. In the Bohr hydrogen atom, the quantum jump from the n = 6 to n = 1 energy level results in the emission of a photon in what part of the electromagnetic spectrum?
   1. X-ray
   2. ultraviolet
   3. visible
   4. infrared
   5. microwave
8. In the Bohr hydrogen atom, the quantum jump from the n = 4 to n = 3 energy level results in the emission of a photon related to which series?
   1. Lyman
   2. Balmer
   3. Paschen
   4. Brackett
   5. Pfund
9. In the Bohr hydrogen atom, the quantum jump from the n = 6 to n = 2 energy level results in the emission of a photon related to which series?
   1. Lyman
   2. Balmer
   3. Paschen
   4. Brackett
   5. Pfund
10. According to the Bohr model of the atom the energy levels of hydrogen-like atoms are
    1. directly proportional to the quantum number n.
    2. proportional to the square of the quantum number n.
    3. inversely proportional to the quantum number n.
    4. inversely proportional to the square of the quantum number n.
    5. independent of the quantum number n.

Answers: 1 (e), 2 (d), 3 (a), 4 (b), 5 (c), 6 (c), 7 (b), 8 (c), 9 (b), 10 (d)

Suggested Conceptual Questions:

Suggested Problem Assignments: