Chapter 26 review


    Conceptual questions
      Section 26.1
      1. For the gold isotope 19479Au, how many neutrons are there?
      2. Easy Use diagrams to show how our understanding of atoms has changed over the past several thousand years.
      3. Easy In Rutherford’s model for the atom, why aren’t the electrons ejected?
      4. Easy Explain how the Rutherford scattering experiment showed that the positive charge in an atom must be concentrated, rather than spread throughout the atom.
      5. Medium In the Rutherford scattering experiment, why do most alpha particles pass through the gold foil without deflection?
      6. Medium In the Rutherford scattering experiment, why are very few alpha particles deflected backward?
      7. Thomson’s experiment showed that cathode rays were deflected by charged plates. He concluded that
        1. cathode rays carried a negative charge.
        2. ordinary light behaved in the same manner.
        3. the gas present in the tube affected the deflection.
        4. different metals emitted different types of cathode rays.
      Section 26.2
      1. A number of commercial products, such as Rainbow Peepholes™ or Rainbow Glasses® that you used in Investigation 26D on page 1525, contain small transmission gratings etched onto clear plastic. What property of light produces the multiple rainbows that you see when you look through one at a small light source?
      2. When matching laboratory emission-line spectra against that for a series of different elements, why is it useful to print one set onto clear, plastic transparencies?
      3. Easy If you wanted to obtain a spectrum of the Sun with a hand-held visual spectroscope while outdoors during a field investigation, how would you do so safely without pointing the spectroscope directly at the Sun?
      4. Easy Describe the connection between energy levels and orbits of the electron and whether or not an atom is a good conductor.
      5. Easy How can you use a hand-held visual spectroscope to distinguish the elements in two different gas discharge tubes?
      1. Distinct energy levels are present in which model of the atom?
        1. Bohr’s quantum atom
        2. Rutherford’s alpha particle
        3. Schrödinger’s cloud model
        4. Thomson’s plum pudding model
      2. Create a presentation on the historical theories and experiments leading to our present model of the atom. Use digital media, such as a slide presentation, and include both text and visual elements to enhance understanding and add interest.
      3. Easy How can emission-line spectra be used to distinguish different elements?
      4. Medium If the electron in a hydrogen atom is in the n = 3 energy level, how many different energies of photons can it emit?
      5. Medium In the de Broglie model of the electron orbit, the electron is treated like a wave. How does this address the question raised by Bohr’s model of why electron orbits are quantized?
      6. Medium Why are energy levels usually written as negative energies?
      7. Medium When identifying elements by their spectra in Investigation 26D on page 1525, you first matched spectra for individual gas discharge lamps and later matched spectra with the Sun and other stars. Why was it more useful to do the investigation in this order and not the other way around?
      8. Easy A physicist measures the wavelengths of light given off by hydrogen gas. Despite taking thousands of measurements, he only measures light at a discrete set of wavelengths, and nothing in between. Explain his results.
      9. Challenging If the electron in a hydrogen atom is in the n = 3 energy level, how many different energies of photons can it absorb?
      10. Challenging A discharge tube ionizes the gas inside—removing one or more electrons from its outer shell—when you apply a voltage across the tube. Why do you think that different discharge tubes require different voltages?
      Section 26.3
      1. Explain how the operation of the laser in a laser pointer is related to quantum theory and the atom.
      2. Easy Describe three technological applications of quantum phenomena.

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