Predict the electron pair geometry, the molecular shape, and the bond angle for a phosgene molec

Predict the electron pair geometry, the molecular shape, and...

Key Concepts

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of molecules based on the idea that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsive forces between them. This theory is integral in determining both the electron pair geometry and the molecular shape of a compound.

Electron Pair Geometry

Electron pair geometry refers to the spatial arrangement of all electron pairs (both bonding pairs and lone pairs) around the central atom. Even when multiple bonds (such as double bonds) are present, they are treated as one region of electron density, which helps in predicting an idealized geometric pattern, such as linear, trigonal planar, or tetrahedral.

Molecular Geometry

Molecular geometry is the actual shape of the molecule as determined by the positions of the atoms, after accounting for the presence of any lone pairs which may distort the ideal electron pair geometry. This results in molecular shapes like bent, trigonal pyramidal, or trigonal planar, depending on the distribution of bonding pairs and lone pairs around the central atom.

Bond Angles

Bond angles are the angles between adjacent bonds that emerge from the central atom. These angles are influenced by the repulsions between electron pairs, with adjustments occurring due to variations in electron density, such as those found in multiple bonds. The ideal bond angles predicted by electron pair geometry can be slightly altered by these repulsive forces, leading to observable deviations in molecular structures.

Transcript

00:01 Hi everyone in this video we're going to be talking about vesper and how vesper allows us to determine the electron pair geometry, the molecular shape, as well as the bond angles of a given molecule.

00:13 So what is vesper? vesper stands for vailantial electron repulsion theory.

00:20 And as i just mentioned a second ago, it allows us to predict the geometry of individual molecules.

00:26 For the number of lone pairs that are present on the central atom and as well as the number of bonds that are present on your central atom.

00:33 So if we wanted to determine the accurate shape, the molecular geometry, molecular shape of a molecule, what we need to do if we wanted to start off a little bit more simplistic approach is we need to start off by drawing the lewis structure and not really worry about the accuracy of our drawing.

00:52 And then using vesper theory, i have a chart here that's going to help us a moment and guide us and then help us determine what the true actual shape is going to be looking like, right? so let's go ahead and get started with that.

01:06 We have here an example, ccl2o.

01:09 This is an example of a phos gene.

01:11 So let's go ahead and get started with drawing the lupus structure.

01:14 So we do have a carbon atom present in this molecule.

01:18 So whenever we have a carbon present, we're always really going to be trying to start drawing the carbon as a central atom.

01:25 Because carbon does have a capability of making a couple of bonds, it can make four, right? so because it can make multiple bonds, we usually try to start that off as the central carbon.

01:36 So let's go ahead and draw carbon here.

01:39 And let's go ahead and start drawing its valence electrons.

01:42 It's going to have four valence electrons.

01:45 And so now let's go ahead and start drawing everything else around it.

01:48 So let's go ahead and just put the oxygen at the top.

01:51 Again, the way i draw my lewis structures is i always try to fulfill the octets for pretty much everything except the central atom.

02:01 It just depends on how it goes, but we'll go ahead and start drawing everything and fulfilling their octets and then we'll edit everything as we go.

02:10 That's just the way i do it.

02:11 You may do it a different way.

02:13 Maybe this way is a little bit confusing for you.

02:15 But hopefully once you see the way that i do it, maybe you'll click.

02:20 So i have everything here.

02:22 Now, as you can see, and you can always double check by counting the number of electrons that are present around each atom.

02:28 But as far as the octet for oxygen and the two chlorine atoms, those are all fulfilled.

02:35 But however, you can see the octet for carbon, it's not quite there yet, right? we have two, four, six, actually seven electrons.

02:43 So we're going to need to do a little bit of altering stuff.

02:48 Right so what we can do every time i see this um this thing happening i always like to try to make double bonds and see if that fixes anything um so i'll go ahead and erase that lone electron at the bottom and i'm going to erase a lone pair at the top from this oxygen and we are going to make a double bond at the top and now keep in mind um this is actually a good thing for oxygen it likes it if you can you're rather better off trying to make a double bond with an oxygen rather than a chlorine.

03:25 Just because with chlorines, chlorines because they're halogens, and they only need one more electron to fulfill their octet...

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