The following molecules contain polar covalent bonds. Which of them are polar molecules and whic

The following molecules contain polar covalent bonds. Which...

Key Concepts

Net Dipole Moment

The net dipole moment is a measure of the overall polarity of a molecule. It results from the vector sum of all the individual bond dipoles, and it determines whether a molecule behaves as polar (with a permanent dipole moment) or nonpolar (with dipole moments that cancel out).

Molecular Symmetry

Molecular symmetry involves the spatial distribution of bonds and lone pairs around the central atom. High symmetry in a molecule can lead to cancellation of individual bond dipoles, resulting in a nonpolar molecule despite the presence of polar bonds.

Molecular Geometry

Molecular geometry refers to the three?dimensional arrangement of atoms in a molecule as determined by VSEPR theory. The shape of a molecule influences how individual bond dipoles vectorially add together, which is critical in determining whether the molecule has an overall dipole moment.

Polar Covalent Bonds

Polar covalent bonds occur when atoms share electrons unequally due to differences in electronegativity. This unequal sharing creates bond dipoles, where one end of the bond is partially negative and the other is partially positive, setting the foundation for molecular polarity.

Transcript

00:01 In this problem, we are told that we need to determine which of the following molecules are polar and non -polar.

00:06 So we've got ccl4, chcl3, co2, h2s, and so2.

00:13 So first we'll start by drawing these out.

00:15 So we've got ccl4, carbon bonded to four other things.

00:21 So carbon, carbon, on these two chlorine.

00:31 So here we've got a stable molecule.

00:34 Each of our chlorines has a full valent shell.

00:37 Our carbon does two.

00:38 It's got four bonds.

00:40 It's happy.

00:41 So now we see we've got four polar bonds, all in the direction of chlorine.

00:46 But we want to determine if the overall molecule is polar.

00:49 So if we do this to all of these, we can see that we've got a negative charge on the outside of the atom and a positive area where the carbon is.

01:00 But we can't say that this molecule is polar because in the end we've got a positive charge that's surrounded by a negative charge.

01:09 So in order to have polarity, we'd have to have an area that's partial positive that's exposed in an area that's partial negative that's exposed.

01:17 So in this molecule, we only have a partial negative area on the outside of the molecule.

01:22 So we would say that this molecule is non -polar because there's no, the charge is not uneven.

01:28 The entire molecule appears to be partially negative on the outside.

01:33 So now we go to our second molecule.

01:35 We've got something similar.

01:36 We've got carbon bonded to four things.

01:38 We've got a hydrogen and we've got three chlorines.

01:46 We've got chlorine, chlorine, chlorine, and then a hydrogen up the top.

01:50 So if we were to do the same thing on this molecule, we'd see that we actually have three partial negative regions.

01:58 But in this one, we also have a partial negative regions.

02:01 Positive region where this hydrogen is.

02:05 So in 3d space, and this molecule would appear to have a negative area down on this end of the molecule and a positive area up here on this side, whereas the other one that we just looked at would be negative all around it.

02:19 So this one is polar because we have this partially negative area that's exposed and this partial positive area that's exposed.

02:28 So this molecule has a dipole in the direction of the three chlorines.

02:34 And it would be this way, no matter where we put the hydrogen, the area with the hydrogen would be the partial positive region.

02:40 So up here, and this area is the partial negative region down here.

02:44 So our second molecule is polar.

02:49 And our first one, write this out, is non -polar.

02:52 No polar.

02:53 It is non -polar.

02:55 All right.

02:57 So now that we've drawn those out, we can go to our second set.

03:00 We've got co2.

03:03 So we've got carbon bonded to two oxygens.

03:07 And oxygen needs to have two bonds to have a formal charge of zero and carbon needs to have four bonds regardless.

03:13 So we'll add two bonds and two lone pairs to each of these.

03:19 And if we're to look at this molecule, we again have something similar to the first molecule and second.

03:25 We have partial positive region on the carbon and the partial negative region on the oxygen...

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