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Homework Help: X-M-X angles in MX6

  1. Apr 20, 2015 #1
    1. The problem statement, all variables and given/known data
    The question says:
    Find the number of X-M-X angles in MX6, which has an octahedral geometry.

    2. Relevant equations

    3. The attempt at a solution
    To do this question , I used p&c .
    Since there are 6 X in MX6 and we have to choose two of them . Therefore total number of M-X-M bonds will be 6C2=15.
    But the solution says that it is 12. When I saw it , I noticed that they had missed the opposite M-X-M bonds. So why had they(the solution makers) not counted those bonds? Are they wrong here ?
  2. jcsd
  3. Apr 21, 2015 #2


    User Avatar

    Staff: Mentor

    I can't think of a good answer to your question. We typically speak only about angles between adjacent bonds, but technically counting angles between non-adjacent bonds is not a mistake if the question is worded just "count angles between bonds".
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