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Homework Help: Energy and periodic trends

  1. Oct 30, 2006 #1
    Out of KF, NaF, and RbCl, does NaF have the shortest ionic bonds as well as highest lattice energy, and RbCl have the lowest melting point?

  2. jcsd
  3. Oct 30, 2006 #2
    It doesnt look like you've done much work on this... Read your chemistry book it will tell you all of these trends in the corresponding sections. You need to show at least some effort even if its not the correct answer.
  4. Oct 30, 2006 #3
    I did, sorry. I just didn't type it all. I read through the trends, and just want to make sure I interpreted them correctly. I was under the impression tha the shorter bonds and highest lattice energy would be the same, because the increased lattice = stronger bonds, and the strong bonds are a high energy, and the shorter they are, the stronger they are.

    Sorry that it was taken that way. GOsh, I feel stupid!
  5. Oct 30, 2006 #4
    What do you think, and why? Show your attempt to solve this problem.
  6. Oct 30, 2006 #5
    Hi Geoff
    I explained my reasoning in the message above you. I thought that the highest lattice and shortest bonds correspond, and I know that as you move up and to the right that they are at the strongest - therefore because F is the farthest and Na is higher than K, I chose NaF.

    For the lowest melting point, I was under the impression it would be the opposite (descendig and towards the left).
  7. Oct 30, 2006 #6
    Bond length is determined by a number of factors, which, as Steve said, should be detailed in your text. Consider bond lengths of each ion and electronegativities. This page might aid your understanding.

    Melting point is directly proportional to intermolecular forces. The more energy it takes to break the bonds between molecules, the higher the melting point.
  8. Oct 30, 2006 #7
    Thanks for the link. I do not understand it, but thank you for your help.
  9. Oct 30, 2006 #8
    Well, we'll do what we can until you do understand. First of all, do you have a chart of trends in your text?
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