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Omniscience

  • 2 years ago

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?

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  1. halcy0n
    • 2 years ago
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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.

  2. jwheele1
    • 2 years ago
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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.

  3. Omniscience
    • 2 years ago
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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?

  4. jwheele1
    • 2 years ago
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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.

  5. Omniscience
    • 2 years ago
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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

  6. jwheele1
    • 2 years ago
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    http://www.green-planet-solar-energy.com/images/PT-small-electroneg.gif

  7. jwheele1
    • 2 years ago
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    What about this link: http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/Polar_Or_Nonpolar.html

  8. Omniscience
    • 2 years ago
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    that will be hard tho; to remember the electronegativity of all elements..

  9. jwheele1
    • 2 years ago
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    this is true....i dont think any teacher would expect that. With out the chart, that method is dead

  10. jwheele1
    • 2 years ago
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    but it is easy

  11. jwheele1
    • 2 years ago
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    with the chart

  12. jwheele1
    • 2 years ago
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    all ionic bonds are polar right?

  13. jwheele1
    • 2 years ago
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    what about this: http://preparatorychemistry.com/bishop_molecular_polarity.htm

  14. Omniscience
    • 2 years ago
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    well i would like a method without the electronegativity chart

  15. Omniscience
    • 2 years ago
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    (if possible)

  16. jwheele1
    • 2 years ago
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    that last link i believe is that kind of method...without the chart

  17. Omniscience
    • 2 years ago
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    i read it..stil needs the chart

  18. jwheele1
    • 2 years ago
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    lame...ok one sec

  19. halcy0n
    • 2 years ago
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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

  20. jwheele1
    • 2 years ago
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    I think I asked my teacher if there was a way and he said no...

  21. Omniscience
    • 2 years ago
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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?

  22. jwheele1
    • 2 years ago
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    well metals and non metals make inonic bonds

  23. jwheele1
    • 2 years ago
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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

  24. jwheele1
    • 2 years ago
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    bottom left is real small.....top right of table is real big

  25. jwheele1
    • 2 years ago
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    Fr = 0.7 F = 4.0

  26. benjaminf
    • 2 years ago
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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.

  27. Gochi
    • 2 years ago
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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

  28. Omniscience
    • 2 years ago
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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.

  29. Sheng
    • 2 years ago
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    it's based on what elements comprise the structure and also on the molecular structure.

  30. Omniscience
    • 2 years ago
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    well how can you see it from the molecular stucture?

  31. Sheng
    • 2 years ago
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    a simple way to see if you can make the 2 sides balance

  32. Omniscience
    • 2 years ago
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    For example, Bromine Br_2' how are able to balance/ see it?

  33. Sheng
    • 2 years ago
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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

  34. Sheng
    • 2 years ago
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    so another example, NaCl, one side has Na other side Cl, 2 different elements, thus polar

  35. Sheng
    • 2 years ago
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    this applies only to certain molecules though, it's just a simple way of looking at things

  36. Omniscience
    • 2 years ago
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    okay i got it. what about molecules is there a legit way?

  37. Omniscience
    • 2 years ago
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    about other molecules*

  38. Sheng
    • 2 years ago
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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.

  39. Sheng
    • 2 years ago
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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

  40. Omniscience
    • 2 years ago
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    i got it thanks.

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