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Communications
This Week's Puzzle

This assignment is due before 9 AM, Friday, April 13th, 2001. Good Luck!

  • This puzzle is worth 5 points of extra credit.
  • Answers must be accompanied by valid reasoning. Unlike the tests, the answer alone isn't enough!
  • Every so often, the first student to submit a correct answer will recieve the stylish Chemistry Nomenclature Flash Cards
    (or a better prize when Dr. Blake can get his hands on some better prizes!).
  • Please enter your solution in the text area at the bottom of this page. DON'T FORGET TO GIVE YOUR NAME!

"Writing the Rule: Which is the Central Atom?"

Due 9:00 AM Friday, April 13, 2001

Many teachers will tell us to memorize rules without trying to understand why the rule works. Solubility rules for ionic compounds can be understood in terms of charges and sizes of ions. This is helpful, because if you forget the rule, you can still figure out the solubilities from the principles.


1. You may remember from lecture that we talked for a while about what kinds of structures we could make from three balls. If you had a collection of balls of three different colors, how many different three ball structures could you build based on a linear structure? Describe each one.

  • If these three colored balls represented C, N and S, the structures you just built could represent isomers of NSC-.

    2. Describe the most stable isomer(s) of NSC-. Why is(are) your structures the best?

    3. For the best structure(s), which atom is central? Why? Be sure to include all the best resonance structures for the good isomer.

    4. What rule would you write for the seletion of the central atom in molecules and ions? What fundamental atomic property guides your selection of the central atom?
    Don't forget to explain your answer as clearly as possible.


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