Predict the electron pair geometry, the molecular shape, and the bond angle for a hydrogen sulfi

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

Key Concepts

Molecular Shape

Molecular shape, or molecular geometry, is the spatial arrangement of only the bonded atoms in a molecule, after taking into account the positions of the lone pairs. While the electron pair geometry considers both bonding and nonbonding electron pairs, the molecular shape is based solely on the position of the atoms, which may be altered from the ideal geometry due to the presence of lone pairs.

Bond Angle Adjustments

Bond angles are the angles between adjacent bonds as determined by the electron pair geometry. However, the presence of lone pairs, which exert a stronger repulsive force than bonding pairs, can reduce the bond angles relative to the ideal geometric values. This adjustment is a key prediction of VSEPR theory for molecules containing lone pairs.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the shape of individual molecules based on the extent of electron-pair electrostatic repulsion. According to this theory, electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion, which in turn determines the overall geometry of the molecule.

Electron Pair Geometry

Electron pair geometry refers to the three?dimensional arrangement of all electron density regions (both bonding and lone pairs) around the central atom. This geometry provides the structural framework from which the shape of the molecule is derived, and it is predicted by considering the total number of electron pairs present.

Transcript

00:01 Everyone in this video we're going to be talking about vesper theory, which is the valence shell electron repulsion, and how we can use that theory in order to help us determine the electron -paired geometry, the shape as well as the bond angles of a given molecule.

00:19 So i don't know, for the definition of valent shell electron repulsion, what it allows us to do really is that it predicts the geometry of individual molecule.

00:30 Just based on number of loan pairs and bonds within.

00:33 So if we wanted to take something like, for example, that hydrogen sulfide, so the formula would be h2s.

00:45 And we wanted to know using vesper theory, election pair geometry shape as well as its bond angles, well, we have to start by drawing the loose dot structure.

00:57 And so when we have something like this, we know that based on the drawing here, sulfur is going to have to go in the middle.

01:06 So let's start by actually just drawing the molecule itself.

01:09 So we have sulfur.

01:11 We know that sulfur is going to want to make at least four bombs.

01:18 That's the max they can make.

01:19 So it's going to have like around it a total of eight electrons, right? but the thing here is that we only have two hydrogen atoms.

01:28 So those are only going to take up about four of those electrons overall, right? so we can just go ahead and do, we can do this.

01:40 Let me go ahead and make that a little bit straighter here.

01:44 We're just drawing it.

01:44 We're not trying to make it necessarily accurate for the moment.

01:49 So we see here, let's count the number of electrons that are around sulfur.

01:53 Remember, each bond itself, it counts as two electrons.

01:57 That's two than four.

01:59 So we're missing four more electrons.

02:01 So those other four electrons are going, we're going to have to put them on sulfur as longed pairs.

02:07 So we're going to do one two, one two.

02:11 Now let's count the number of electrons that are around sulfur.

02:15 We have two, four, six, eight.

02:17 Perfect.

02:17 That satisfies that octet rule.

02:20 And it satisfies the octet rule for hydrogen.

02:25 The octet rule for hydrogen, if we recall, is not.

02:29 Necessarily an octet for it by tradition.

02:33 Its octet is two electrons, not eight like a lot of the other elements in the periodic table.

02:38 So the octets for every single atom and dihydrogen sulfide are fulfilled.

02:44 Now, we just drew this molecule just so we can draw and we can get a feel for how many bonds are being actually made and how many lone pairs are actually present...

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