1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Explanation for exception in a trend? - Chemistry

  1. Feb 29, 2016 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    I have to explain why the boiling point generally increases from groups 14-16 but drops from 16-17, my answer is that every molecule in the the 17th group has only two atoms, meaning there are less protons in the molecule causing a weak london dispersion force. I'm in a relatively low level so I think this answer may do but does anyone have a better explanation or an addition to mine? Any help is appreciated
    Last edited: Feb 29, 2016
  2. jcsd
  3. Mar 1, 2016 #2


    User Avatar

    Staff: Mentor

    Boiling points increase is observed in all groups, the only exception being molecules from the first period.

    Your explanation doesn't touch higher than expected boiling points of ammonia and water.

    Hint: ammonia, water and hydrogen fluoride all have sticking out free electron pairs. Do you know any kind of interaction that could utilize them?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted