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Omniscience Group Title

How to distinguish between polar and non-polar molecules/compound? For instance, one that you have not studied before but have to know if its polar or non-polar. Can you distinguish it from the basic structure of the molecule? For instance, Bromine Br_2; at first I thought it was polar but then its not non-polar..so how can you tell?

  • one year ago
  • one year ago

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  1. halcy0n Group Title
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    You can instantly tell if a molecule is polar if you look at the electronegativity differences between two differing atoms. The larger the difference between electronegativity values, the more polar the molecule is.

    • one year ago
  2. jwheele1 Group Title
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    halcyon is right. Do you have an electronegativity chart? Some are different from others. IS there one in your text book? If not I can find you one, but its better to use what your teacher supplies you with.

    • one year ago
  3. Omniscience Group Title
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    But a non-polar molecule would have an electrongativity differences as well; i think. and electronegativity charts are not provided in exams here is it possible to distinguish it from the structure of the molecule?

    • one year ago
  4. jwheele1 Group Title
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    Not sure about how to find the answer from structure. "But a non-polar molecule would have an electrongativity differences as well; i think." You are right. The way you determine the status is to see to which degree of difference is apparent.

    • one year ago
  5. jwheele1 Group Title
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    http://4.bp.blogspot.com/__E1v9cAjiVs/TMjVxHpJbWI/AAAAAAAAABU/JW1YuKX9-s4/s1600/electronegativity+table.jpg

    • one year ago
  6. Omniscience Group Title
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    What if I dont know anything about the molecule; like if its polar or non-polar how am i able to distinguish? If i remember correctly, you can determine it by the structure..but i cant remember how

    • one year ago
  7. jwheele1 Group Title
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    http://www.green-planet-solar-energy.com/images/PT-small-electroneg.gif

    • one year ago
  8. jwheele1 Group Title
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    What about this link: http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/Polar_Or_Nonpolar.html

    • one year ago
  9. Omniscience Group Title
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    that will be hard tho; to remember the electronegativity of all elements..

    • one year ago
  10. jwheele1 Group Title
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    this is true....i dont think any teacher would expect that. With out the chart, that method is dead

    • one year ago
  11. jwheele1 Group Title
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    but it is easy

    • one year ago
  12. jwheele1 Group Title
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    with the chart

    • one year ago
  13. jwheele1 Group Title
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    all ionic bonds are polar right?

    • one year ago
  14. jwheele1 Group Title
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    what about this: http://preparatorychemistry.com/bishop_molecular_polarity.htm

    • one year ago
  15. Omniscience Group Title
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    well i would like a method without the electronegativity chart

    • one year ago
  16. Omniscience Group Title
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    (if possible)

    • one year ago
  17. jwheele1 Group Title
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    that last link i believe is that kind of method...without the chart

    • one year ago
  18. Omniscience Group Title
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    i read it..stil needs the chart

    • one year ago
  19. jwheele1 Group Title
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    lame...ok one sec

    • one year ago
  20. halcy0n Group Title
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    All ionic bonds are polar. Electronegativity differences are taken into account with covalent bonds. If it's a compound such as F2 then no, it's not polar cause of the same electronegativity

    • one year ago
  21. jwheele1 Group Title
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    I think I asked my teacher if there was a way and he said no...

    • one year ago
  22. Omniscience Group Title
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    well what if you dont know if its an ionic bond or not..how would you know if its polar or non-polar?

    • one year ago
  23. jwheele1 Group Title
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    well metals and non metals make inonic bonds

    • one year ago
  24. jwheele1 Group Title
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    You can always make an educated guess if you know if an element is metal or non metal or if you know if an element is on the left or right or top or bottom of the per table

    • one year ago
  25. jwheele1 Group Title
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    bottom left is real small.....top right of table is real big

    • one year ago
  26. jwheele1 Group Title
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    Fr = 0.7 F = 4.0

    • one year ago
  27. benjaminf Group Title
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    It's entirely about the structure, like you were thinking! Basically symmetry means non-polar and asymmetry means polar. So Br2 has two atoms with the same EN; you can imagine their electron withdrawing strength canceling out one another's pull so that there's no net pull in the structure and the whole thing is non-polar. In contrast, something like CO would have a net polarity because even if you can't remember what the EN of C of O is, you still know that one half of that molecule is going to pull the electrons a little more than the other. That gives the molecule a net polarity. It helps if you just draw a little arrow pointing in the direction of the Electron withdrawing activity. Then you can see if there's a net pull or if there are arrows that cancel one another out.

    • one year ago
  28. Gochi Group Title
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    u cn find d difrnc simply by evaluatng d electronegativity o strucure. evn the aarangemnt in d periodic table l gv u an idea of the polarity b/w molecules,atoms,elemnts

    • one year ago
  29. Omniscience Group Title
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    okay, thanks benjaminf but for the structure; is it the molecular structure? the chemical formula structure or what? They just look symmetrical to me.

    • one year ago
  30. Sheng Group Title
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    it's based on what elements comprise the structure and also on the molecular structure.

    • one year ago
  31. Omniscience Group Title
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    well how can you see it from the molecular stucture?

    • one year ago
  32. Sheng Group Title
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    a simple way to see if you can make the 2 sides balance

    • one year ago
  33. Omniscience Group Title
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    For example, Bromine Br_2' how are able to balance/ see it?

    • one year ago
  34. Sheng Group Title
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    if you cut the molecule in 1/2, one side will have 1 Br and the other another Br, so it's balanced thus non-polar

    • one year ago
  35. Sheng Group Title
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    so another example, NaCl, one side has Na other side Cl, 2 different elements, thus polar

    • one year ago
  36. Sheng Group Title
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    this applies only to certain molecules though, it's just a simple way of looking at things

    • one year ago
  37. Omniscience Group Title
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    okay i got it. what about molecules is there a legit way?

    • one year ago
  38. Omniscience Group Title
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    about other molecules*

    • one year ago
  39. Sheng Group Title
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    yes, you have to look at their electronegativity (how much they attract electrons). If there is high electronegativity differences it's most likely a polar bond (e.g. NaCl). But if they got close to no difference (e.g. C-H), then it's a non-polar bond.

    • one year ago
  40. Sheng Group Title
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    on top of that, you have to use the 1st rule i mentioned above, a polar bond may be cancelled out by another polar bond on the exact opposite side...e.g. CCl4, even tho the C-Cl bonds are polar, the exact conformation of the molecule allows all the polarity to cancel out to 0

    • one year ago
  41. Omniscience Group Title
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    i got it thanks.

    • one year ago
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