CHM101, Section 5, Fall 2000
Third hourly exam, Tuesday 14 November 2000
Chapters 7–9

Instructions:
      Read over the entire exam first. Begin with the questions you feel most confident about. Pace yourself so that you will have time enough to try everything. If you don’t know how to get all the way to an answer, go as far as you can and state how you would approach the rest. And keep your handwriting neat! Use the back of the sheets if necessary.

Definitions (2 points each; 20 points total)
      1. Photon
      2. Line spectrum
      3. Atomic orbital
      4. Orbital angular momentum quantum number
      5. Ionization energy
      6. Aufbau principle
      7. Transition element
      8. Octet rule
      9. Skeletal structure
      10. Electronegativity

Short answers (4 points each; 40 points total)

c = 3.00x10⁸ m s^-1

      1. Show the difference in shapes of an s orbital, a p orbital, and a typical d orbital. Use separate XYZ plots.
      2. When Neptune is 4.4 x 10⁹ km from the earth, how many hours does it take light from Neptune to reach us?
      3. Write the abbreviated electron configuration (1s²2s²2p⁴, etc.) for each of these elements and ions. Use the positional rather than the sequential option.
      (a) B ______________________________________
      (b) K ______________________________________
      (c) As ______________________________________
      (d) Sc³⁺ ____________________________________
      4. Explain why atomic radii increase down a column of the periodic table.
      5. (a) Why are the properties of elements in a transition series relatively similar to one another compared to elements in the main groups of the periodic table?
      (b) Why are the properties of the lanthanides even more similar to one another?
      6. Describe the Rutherford scattering experiment and what conclusions it led to.
      7. Why is the second ionization energy for an element considerably larger than the first?
      8. How do we know that neutrons exist?
      9. Where in the periodic table do you expect to find elements whose atoms can use expanded valence shells to bond with more than four other atoms?
      10. Explain why metals, nonmetals, and semimetals are found in the lower left, the upper right, and intermediate positions of the periodic table, respectively.

Problems (5 points each; 40 points total)

Planck’s constant h = 6.626x10^-34 J s

      1. Niels Bohr discovered that the energy of an electron around a hydrogen atom existed only in discrete states E_n = -B/n², where n is an integer (n = 1, 2, 3.…) and B is a constant. Start from this equation and derive the equation for the difference in energy between final and initial states of an electron, using n_f and n_i, respectively.
      2. Draw a diagram that illustrates the aufbau principle, and show how to use it.
      3. Fill in the blanks with acceptable quantum numbers.
            (a) n = ______, l = 2, m_l = 0, m_s = __________
            (b) n = 2, l = _________, m_l = -1, m_s = -½
            (c) n = 4, l = _______, m_l = 2, m_s = _____________
            (d) n = _______, l = 0, m_l = __________, m_s = ½
      4. Draw the orbital diagram (with the boxes and the arrows) for the V atom.
      5. The laser in a CD player uses light with a wavelength of 780 nm. Calculate the energy of this radiation in joules per photon and in kilojoules per mole of photons.
      6. Use a diagram to show how the potential energy of a system of two hydrogen atoms varies with the distance between their nuclei. Make the distances extend from ∞ to less than the distance of the H–H bond. Show the zones of attraction and repulsion between the atoms, and show how to locate the length of the H–H bond on the diagram.
      7. Draw the Lewis structures for (a) NH₃ and (b) SeF₄.
      8. Draw the Lewis resonance structures for the nitrate ion, NO₃^-.

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