anonymous
  • anonymous
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?
Chemistry
  • Stacey Warren - Expert brainly.com
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jamiebookeater
  • jamiebookeater
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anonymous
  • anonymous
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.
jwheele1
  • jwheele1
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.
anonymous
  • anonymous
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?

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jwheele1
  • jwheele1
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.
jwheele1
  • jwheele1
http://4.bp.blogspot.com/__E1v9cAjiVs/TMjVxHpJbWI/AAAAAAAAABU/JW1YuKX9-s4/s1600/electronegativity+table.jpg
anonymous
  • anonymous
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
jwheele1
  • jwheele1
http://www.green-planet-solar-energy.com/images/PT-small-electroneg.gif
jwheele1
  • jwheele1
What about this link: http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/Polar_Or_Nonpolar.html
anonymous
  • anonymous
that will be hard tho; to remember the electronegativity of all elements..
jwheele1
  • jwheele1
this is true....i dont think any teacher would expect that. With out the chart, that method is dead
jwheele1
  • jwheele1
but it is easy
jwheele1
  • jwheele1
with the chart
jwheele1
  • jwheele1
all ionic bonds are polar right?
jwheele1
  • jwheele1
what about this: http://preparatorychemistry.com/bishop_molecular_polarity.htm
anonymous
  • anonymous
well i would like a method without the electronegativity chart
anonymous
  • anonymous
(if possible)
jwheele1
  • jwheele1
that last link i believe is that kind of method...without the chart
anonymous
  • anonymous
i read it..stil needs the chart
jwheele1
  • jwheele1
lame...ok one sec
anonymous
  • anonymous
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
jwheele1
  • jwheele1
I think I asked my teacher if there was a way and he said no...
anonymous
  • anonymous
well what if you dont know if its an ionic bond or not..how would you know if its polar or non-polar?
jwheele1
  • jwheele1
well metals and non metals make inonic bonds
jwheele1
  • jwheele1
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
jwheele1
  • jwheele1
bottom left is real small.....top right of table is real big
jwheele1
  • jwheele1
Fr = 0.7 F = 4.0
anonymous
  • anonymous
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.
anonymous
  • anonymous
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
anonymous
  • anonymous
okay, thanks benjaminf but for the structure; is it the molecular structure? the chemical formula structure or what? They just look symmetrical to me.
anonymous
  • anonymous
it's based on what elements comprise the structure and also on the molecular structure.
anonymous
  • anonymous
well how can you see it from the molecular stucture?
anonymous
  • anonymous
a simple way to see if you can make the 2 sides balance
anonymous
  • anonymous
For example, Bromine Br_2' how are able to balance/ see it?
anonymous
  • anonymous
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
anonymous
  • anonymous
so another example, NaCl, one side has Na other side Cl, 2 different elements, thus polar
anonymous
  • anonymous
this applies only to certain molecules though, it's just a simple way of looking at things
anonymous
  • anonymous
okay i got it. what about molecules is there a legit way?
anonymous
  • anonymous
about other molecules*
anonymous
  • anonymous
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.
anonymous
  • anonymous
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
anonymous
  • anonymous
i got it thanks.

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