¿Cuál de las moléculas siguientes cree que tendría un momento dipolar distinto de cero? En cada

¿Cuál de las moléculas siguientes cree que tendría un...

Key Concepts

Molecular Symmetry

Molecular symmetry plays a critical role in determining net polarity. In highly symmetrical molecules, the vector sum of the bond dipoles can cancel out completely, resulting in a nonpolar molecule. In contrast, molecules with asymmetrical shapes typically have a net dipole moment because the individual dipoles do not cancel.

Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms within a molecule. The shape of the molecule determines how the individual bond dipoles are oriented. If the geometry is such that the bond dipoles cancel out (for example, in symmetric arrangements), the molecule may have little to no net dipole moment even if the individual bonds are polar.

Dipole Moment

The dipole moment is a measure of the overall polarity of a molecule, arising from differences in electron density between atoms. It is a vector quantity that depends on both the magnitude of the individual bond polarities and their spatial arrangement. In essence, a molecule exhibits a net dipole moment when the individual bond dipoles do not cancel each other out.

Electronegativity Differences

Electronegativity refers to the tendency of an atom to attract electrons in a chemical bond. When atoms with different electronegativities form a bond, the electrons are drawn more toward the more electronegative atom, creating bond dipoles. These differences are fundamental to determining whether a bond is polar.

Transcript

0:00 Good day.

00:02 In this question we've been given a list of molecules and we need to identify which molecules have dipole moments.

00:10 So to identify the dipole moments, we also need to identify the molecular structures of these compounds.

00:20 So we have drawn the little structures and then identify the molecular structure.

00:24 So i've put down here a table of vsepr structures.

00:28 So let's begin with question a, which is cs2.

00:36 So we need to calculate the total number of valence electrons for cs2.

00:41 And so that's four electrons for carbon plus six valence electrons for sulfur times two sulfur atoms and this will give us a total of 16 valence electrons.

00:57 Then we put down carbon in the middle because it's the least electronegative sulfur on either end.

01:04 And we then put our bonding electrons.

01:07 Then we fill the octates of the sulphurs.

01:14 Now in doing so, we've got 16 electrons, but carbon does not have a full octate.

01:18 So we'll have to move these two electrons and those two electrons as well from sulfur to form double bonds.

01:28 So now that is our stable lewis structure.

01:33 And looking at the lower structure and we identify that there are two regions of electron density and that will give us a linear molecular structure, which there are zero lone pairs.

01:49 Now this is a linear structure, molecular structure, and therefore it will not have any dipole.

01:56 So this one has no dipole moments.

02:02 This is because the surface are 180 degrees apart.

02:08 Apart from each other and therefore they cancel out the dipole moments.

02:17 And then looking at question b, we have ses2.

02:24 So calculating the valence electrons for ses 2, that's six valence electrons for s .e.

02:30 Plus six valence electrons for sulfur times two sulfur atoms.

02:35 This gives us a total of 18 valence electrons.

02:43 So s is the least electron negative.

02:45 We put it in the middle, and then sulfur on either ends.

02:49 All right, so then we put our bonding electrons and we fill the outer octates of the sulphurs.

03:00 And this will give us total of 14 electrons.

03:07 But now, se is not fully balanced.

03:10 Oh, yeah, sorry, and the two more.

03:12 So now that's 16.

03:16 So that's 24, 6, 8, 10, 12, 14, 16, 18 electrons now.

03:21 So we'll need to remove these two electrons from sulphur and then form a double point over there.

03:31 So now we'll notice that this from the molecular structure, we have three, the number of three electron pairs and one lone pair, therefore this is bent.

03:44 This has a bent molecular structure.

03:48 And because it is bent at less than 120 degrees, therefore there will be a dipole moment for this molecule.

04:08 Then looking at c, this is c, c, cl2, f2, calculated in the total number of valence electrons for this molecule at before, plus 6 times 2 with chlorine atoms, plus 6 times 2 for 4 fluorine, sorry, it's actually seven, seven valence electrons for chlorine and fluorine.

04:52 This will give us a total of 32 valence electrons...

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