Which of the following molecules would you expect to have a resultant dipole moment (μ) ; (a) F2

Which of the following molecules would you expect to have a...

Key Concepts

Molecular Geometry and Symmetry

The three-dimensional arrangement of atoms in a molecule (its geometry) and the symmetry of that arrangement play a crucial role in determining whether the bond dipoles cancel out or add up to give a net dipole moment. Highly symmetric molecules tend to have their individual bond dipoles cancel, resulting in a nonpolar molecule, while lower symmetry usually leads to a net dipole.

Electronegativity Differences

Electronegativity differences between bonded atoms are the source of individual bond dipoles. When atoms with significantly different electronegativities form a bond, the electron density is unevenly distributed, creating a polar bond. The overall polarity of the molecule depends on both these differences and how the bonds are spatially arranged.

Net Dipole Moment

The net dipole moment of a molecule is the vector sum of its individual bond dipoles. It represents the overall polarity of the molecule and is influenced by both the magnitude of the electronegativity differences in the bonds and the molecular geometry that determines how these dipoles combine.

Transcript

00:01 All right, so we have molecules given to us, and we're trying to figure out which molecules have a result in dipole moment, and which molecules do not have a result in dipole moment.

00:10 So we're just initially looking for this.

00:13 The easiest way to do this is to figure out if something is polar or non -polar, and that will tell you if something has a resultant dipole moment.

00:21 So if it's polar, it means that there's uneven distribution of electrons in the molecule, and there's going to be a result in dipole moment.

00:30 If it's non -polar, all the dipole moments are going to cancel, even if there's some, or sometimes there's none, because there's even distribution of electrons, and there's going to be no result in dipole moment.

00:45 So we have to draw it and then figure out whether it's going to be polar or non -polar.

00:48 So let's do that.

00:49 So let's do the first one, f2.

00:52 It's going to be f, and then f, total number of valence elections.

00:55 That's 7 times 2 is 14.

00:57 Connect, we have used 2, now we have 12.

01:00 And then distribute to 4, 6, 8, 10, 12.

01:05 This right here is non -polar.

01:07 It is equally symmetric.

01:09 There is not one that is more electron -negative than the other.

01:12 They're equally election -negative.

01:14 So this is going to have no electronegativity difference.

01:18 So f2 goes right here.

01:20 There is no dipole moment present in the molecule at all.

01:24 So then we go to no2.

01:30 Let's draw no2.

01:32 So we have 5 valence electrons plus oxygen is 6, and there's two of them.

01:37 So that's 12 plus 5 is 17.

01:41 So we go n -o -o -connect.

01:44 We have used 4.

01:46 There's 2 here and 2 here.

01:48 So we'll give us 13.

01:51 And then the distribute, 2, 4, 6, 8, 10, 12, and then 13.

02:01 So there's a couple of things going on here.

02:05 The first one that you will notice is we have an even number of valence electrons is going to be a radical molecule, right? so what we're going to do is we're going to still get that nitrogen to be as close to 8 as possible.

02:19 So we're going to give it 7, so i'm going to make a double 1.

02:21 And you could go either way, right? but we are going to have an uneven number of electrons in the nitrogen.

02:27 Now, because oxygen is much more electron negative than the nitrogen is, and because this is a bench shape, this is going to be polar.

02:36 So, no2 will go right here, right? so there is a dipole moment this way, and this way, if we were to show it with arrows, but there's an electron right here.

02:48 So this is a bench molecule, and there's going to be an even distribution of electrons.

02:52 So then we go to bf3.

02:57 So it's going to be boron, flooring, flooring, flooring.

03:03 We have seven times three.

03:06 Each of those are seven, there's three of them, plus three, four, boron.

03:09 So it's going to be 24 electrons.

03:12 Connect.

03:13 We have used two, four, six.

03:16 Now we have 18 left.

03:18 So two, four, six, eight, ten, twelve, fourteen, sixteen, eighteen, eighteen.

03:24 And we're done.

03:26 Remember that boron can, it's an exception to the octar rule.

03:30 It is stable with six and not with eight.

03:33 Now, there is a difference in electric negativity between the boron and the flooring, and there is a net dipole moment in that bond, but they'll cancel because this molecule is symmetrical, so this is going to be non -polar.

03:49 So bf3 has no result in dipoleum, right, because the dipole moment is cancel.

03:55 All right, let's go to hbr...

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