Polar Bonds

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Trevor_Ramsey_3H
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Polar Bonds

Postby Trevor_Ramsey_3H » Fri Nov 20, 2020 1:24 pm

Hi, How are you able to determine if a molecule contains polar bonds just by looking at the structure and its atoms.

Sharon Kim 2A
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Re: Polar Bonds

Postby Sharon Kim 2A » Fri Nov 20, 2020 1:29 pm

Usually you should look for symmetry and atoms that have different electronegativities within the structure. If dipole moments do not cancel it is safe to assume there are polar bonds.

Alexandra Ahlschlager 1L
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Re: Polar Bonds

Postby Alexandra Ahlschlager 1L » Fri Nov 20, 2020 1:31 pm

You can determine this by looking at the differences in electronegativity between the atoms; atoms with a large difference in electronegativity will create a dipole and cause the molecule to be polar. For example, in an HF molecule, the large difference in electronegativity would cause electrons to be pulled toward the fluorine atom, generating a dipole and making the molecule polar. Hope this helps!

SelenaDahabreh1D
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Re: Polar Bonds

Postby SelenaDahabreh1D » Fri Nov 20, 2020 1:39 pm

Also, it is helpful to look at lone pairs. I remember there was a problem in the textbook in which we were asked to draw the figure of AsF3 and AsF5. And since the dipole moments cancelled out in AsF3, it was considered to have a lower boiling point because it was no longer polar. On the other hand, AsF3 had a higher boiling point because it had one lone pair so the dipoles did not entirely cancel out.

Lesly Lopez 3A
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Re: Polar Bonds

Postby Lesly Lopez 3A » Fri Nov 20, 2020 1:51 pm

Hi,

The way I do it is to look at the differences in electronegativity between the atoms on the periodic table. When the atoms with a large difference in electronegativity compared to each other then this will create a dipole moment. This is what will cause the molecules to be polar. The large difference in electronegativity would cause electrons to be pulled toward the the low electronegativity atom, forming a dipole and making the molecule polar.

Maya Johnson 2a
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Re: Polar Bonds

Postby Maya Johnson 2a » Fri Nov 20, 2020 2:48 pm

Hi,
I usually look for lone pairs or symmetry when looking to see if a molecule is polar or not. Also, I look to see if the central atom has all the same types of atoms surrounding it, as sometimes if one is more electronegative than the other it cause cause a slight pull of e-.

simona_krasnegor_1C
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Re: Polar Bonds

Postby simona_krasnegor_1C » Sat Nov 21, 2020 4:47 pm

For this, I tend to look at electronegativity and the presence of lone pairs in the lewis structure. Based off of this, we can see which atom wants electrons more and therefore we can see the sharing is not exactly equal, creating a dipole.

Crystal Pan 2G
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Re: Polar Bonds

Postby Crystal Pan 2G » Sat Nov 21, 2020 5:32 pm

You would draw the dipole moments on the lewis structure(by determining en) and then using vector addition, you could see which of the dipole moments cancel.

Kevin Pilcher 3J
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Re: Polar Bonds

Postby Kevin Pilcher 3J » Sat Nov 21, 2020 5:43 pm

The key thing I look for is symmetry in the molecule and after that, I look at the charges. If there is symmetry in both the bonds and charges within the molecule it is likely nonpolar.

Vince Li 2A
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Re: Polar Bonds

Postby Vince Li 2A » Sat Nov 21, 2020 6:32 pm

You would look at the dipoles of the molecules. Remember when Dr. Lavelle mentioned partial positive and partial negative charges. To determine if a molecule is polar, there are multiple strategies you can use. First, you could determine the Lewis dot structure. By looking at the dot structures, you will be able to see the lone pair locations. This is where electrons have the greater electron density, so for example when looking at an H2O molecules, you will see that there are two lone pairs on the Oxygen atom that are in a bent shape. Because the components of the dipole point towards the lone pairs, in that the Oxygen is more electronegative, there is a partial negative charge on the Oxygen and a partial positive charge on the Hydrogen. If the components of the dipoles are going in a specific direction, the molecule is polar.

Mackenzie Van Val 3E
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Re: Polar Bonds

Postby Mackenzie Van Val 3E » Sat Nov 21, 2020 7:45 pm

If a molecule has a symmetric structure with all the same atoms around the central atom (for example, SF6), you can immediately tell that the molecule is non-polar, With molecules that have an asymmetric structure, you can look at the atoms within the molecule and use periodic trends to help you determine polarity; for example, we know O is extremely electronegative based on periodic trends, which can help us determine that H2O is polar. Also, if a molecule appears to have symmetric structure, but the atoms around the central atom are not the same (for example, in NSF3), then the molecule is likely polar because the charges will not cancel out to zero.

Yolanda_Xing_3A
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Re: Polar Bonds

Postby Yolanda_Xing_3A » Sun Nov 22, 2020 11:20 pm

I would look if the structure is symmetrical for not. If it is asymmetrical, then it is polar. Then use the periodic trends to determine the polarity.

George Hernandez 3I
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Re: Polar Bonds

Postby George Hernandez 3I » Sun Nov 22, 2020 11:36 pm

By the looking at the structure, if the molecule is asymmetrical with bonding, electrons, etc, then it is always non-polar because that means that one side is slightly more positive/negative than the other.

Megan ODonnell 3F
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Re: Polar Bonds

Postby Megan ODonnell 3F » Mon Nov 23, 2020 10:20 am

Usually symmetry, and if you can determine the difference in electronegativities. If the shape of the molecule is mostly symmetrical it is more likely to be non polar.

Annette Fishman
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Re: Polar Bonds

Postby Annette Fishman » Mon Nov 23, 2020 12:49 pm

I look at electronegativity and the presence of lone pairs in the Lewis structure. It is extremely helpful to also draw the atom and indicate all the lone pairs. If the molecule is asymmetrical with bonding, electrons, etc, then it is always non-polar because that means that one side is slightly more positive/negative than the other.

105618850
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Re: Polar Bonds

Postby 105618850 » Mon Nov 23, 2020 1:47 pm

You should examine the dipole moments and observe if they cancel each other out. A more simple way of thinking about polarity is looking at the molecule's symmetry. At times, it will be pretty obvious but sometimes I double check using the scientific method rather than just relying on the visual method.

105618850
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Re: Polar Bonds

Postby 105618850 » Mon Nov 23, 2020 1:50 pm

You should examine the dipole moments and observe if they cancel each other out. A more simple way of thinking about polarity is looking at the molecule's symmetry. At times, it will be pretty obvious but sometimes I double check using the scientific method rather than just relying on the visual method.

Joshua Swift
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Re: Polar Bonds

Postby Joshua Swift » Sun Dec 06, 2020 9:59 pm

If the molecule has different atoms bonded to each other, it will be polar. However, the geometry of a molecule can cancel out these polar bonds and make it nonpolar due to its symmetry.

Joshua Chung 2D
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Re: Polar Bonds

Postby Joshua Chung 2D » Sun Dec 13, 2020 1:11 pm

You look at the geometry and the differences in electronegativity. If there are clear differences that do not cancel out, then the bond is polar.

Yuehan_Wu_3K
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Re: Polar Bonds

Postby Yuehan_Wu_3K » Tue Dec 15, 2020 10:06 pm

If the structure is symmetric, then it's polar.


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