9.2 Polarity | General Chemistry
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- เผยแพร่เมื่อ 4 ก.ค. 2024
- Chad provides a comprehensive lesson on how to determine if a molecule is polar or nonpolar based upon its individual bond dipoles and its molecular geometry. The lesson begins with a review of electronegativity and relative bond polarity. It is then demonstrated that if the bond dipoles in a molecule sum to zero (i.e. "cancel") then a molecule is termed nonpolar, and a good example of this is CO2. It is then shown that if the central atom does not have lone pairs of electrons and if the atoms surrounding it are all the same then it will be nonpolar (as in CO2, BCl3, and CF4). It is also shown that if the central atom has lone pairs of electrons then it will USUALLY be polar (as in SO2, NF3, and H2O), but there are two MAJOR exceptions. If all the atoms surrounding the central atom are once again identical but the molecular geometry is either square planar or linear (linear with 2 bonding and 3 nonbonding electron domains) then the molecule will still be nonpolar (XeF4 and XeF2 are examples of these respectively).
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00:00 Lesson Introduction
00:47 Review of Electronegativity
02:33 Bond Polarity vs Molecular Polarity
08:24 CH2Cl2 is Polar
11:25 CO2, BCl3, & CF4 are Nonpolar
14:23 SO2, NF3, and H2O are Polar
17:48 XeF4 & XeF2 are Nonpolar
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Loved the review on polarity. Just one thing I would like to point out, when you were talking about the polarity of water, you actually drew the dipole lines toward the hydrogens instead of toward oxygen. Best regards.
Well that's embarrassing! But thanks for taking the time to point it out. I'll be sure to pin this comment for possible future puzzled students to see!
The general rule you give at 20:02 is SO HELPFUL and good to know! Makes everything much more simple. Thank you.
You're most welcome.
17:12 sir I think in case of water you draw dipole moment vectors in wrong direction. Thanks for these amazing lectures though
HAPPY TEACHING, CHAD! GREAT CHANNEL!
Glad you think so!
Are XeF2's electrons 120 degrees apart? And if so, does that mean they cancel out or how come it does not seem like they play a role in polarity?
the lone pairs are indeed 120 degrees apart and spread equally therefore cancelling each other out
So clear! thanks!
You're welcome.
Thanks Mister Chad this lesson was bothering me thank you Mr.Chad
You're very welcome ANGELO Son! Glad it was a timely release!
chad u are such a chad for this i preciate u
Glad to hear it!
Thank God I found a chemistry saviour 🙏
Glad you found us - Happy Studying!
Thank you so much chad
You're welcome
I'm so confused because in C2H2CL2 my professor said that because the vectors started and ended in the same place when you draw them out, that they would indeed cancel therefore would conclude no dipole moment which means also it is a non polar molecule. Could you clarify please.
Hi Elizabeth! I think you may be confusing CH2Cl2 (in the video) and C2H2Cl2 covered by your professor. Note that these are not the same compound. CH2Cl2 has a single carbon which is sp3 hybridized and bond angles of approximately 109.5 degrees. If the Cl atoms were 180 degrees apart, it would be nonpolar, but since they are just 109.5 degrees, it is polar.
C2H2Cl2 has 2 carbon atoms that are double bonded to each other. There are actually 3 possible isomers for this compound: 2 are polar and 1 is nonpolar. If both Cl atoms are bonded to one carbon and both H atoms to the other, then the molecule will be polar. The other option is for each carbon to be bonded to 1 Cl and 1 H atom, but there are still two isomers possible, cis and trans. The cis isomer has the Cl atoms oriented only 60 degrees apart and is still polar. But the trans isomer has them exactly 180 degrees apart and is nonpolar and I'm guessing that this might be the isomer your professor covered. Toward the bottom of the page, you can see a comparison of these last two at the following link: testbook.com/chemistry/physical-properties-of-alkenes
Hope this helps!
@@ChadsPrep my apologies, you’re right. I’m using your videos to quickly review before I take the exam and overlooked that. 🤦🏻♀️
@@yagirlliizziie Hope you do well on your exam.
Perfect
Thank you