Molecular Geometry (Simplified) - Video Tutorials & Practice Problems

Molecular Geometry (Simplified) Concept 1

Now the molecular geometry is seen as the true shape of a molecule. That takes into account differences in a repulsion between lone pairs and surrounding elements, we're gonna say because of this, they treat lone pairs and surrounding elements as different. Yeah, So let's take a look at two electron systems. So to electronic group systems were going to say this is where central elements with two electronic groups have zero lone pairs to give only one possible molecular geometry. Right? So the number of electrons says to the number of bonding groups would be too, and a number of lone pairs on the central element would be zero. So here to some good examples, we have beryllium chloride. Here we have carbon dioxide and here we have hydro scion IQ acid and all of them, the central element is connected to two bonding groups. And again, it doesn't matter if you're double bonded, triple bonded or single bonded to that surrounding element. It only counts once the visible visual representation is we have our central element and we have to surrounding groups or to surrounding elements. Because of this, we're going to see the molecular geometry would be linear. So when it comes to our molecular geometry, where the electron group number is two, you can only have a linear shape.

Molecular Geometry (Simplified) Concept 2

here we're going to say that central elements with three electron groups can have either zero or one long pair, which gives us two possible molecular geometries. All right. So we have three electron groups. And the possibilities are you have three bonding groups surrounding elements and zero long pairs. Or you could have two bonding groups and one lone pair. Remember adding up your bonding groups and your lone pairs together gives you back the number of electrons groups. So with three bonding groups and zero lone pairs, we have this example carbon is connected to three surrounding elements. The visual representation will be our central element in black and these three surrounding elements here. This would be tribunal or tribunal plainer or planner. Let's look at when you have two bonding groups in one lone pair Here we have in the center. It has to bonding groups in the form of those chorines and has one lone pair here. The representation would look like this here, you would have to add in the fact that the lone pair is there which is causing this bending of the bond. Now this particular shape goes by a few different names. You might see it written is bent. Mhm. Others might see it written as V shaped. Yeah. Or you might see it as angular. Yeah. Now the first to kind of make sense. It's not a straight line, it's bent. Also V shape makes sense because it's an upside down. V angular is a little bit tricky but realized here that any one of these three names are associated with this particular shape where you have to bonding groups and one lone pair on the central element. And remember when you have three electron groups total, you can either have this as your molecular geometry or this as your molecular geometry.

Molecular Geometry (Simplified) Example 1

determine the molecular geometry for following molecule. We have boron in three. Corinne's. Alright so boron is in group three, A. Chlorine is in group seven a. And there are three of them. So that's a total of 24 valence electronics. We place boron in the center and it's gonna form single bonds with the surrounding elements. Remember to provide enough electrons to the surrounding elements. So they each follow the octet rule where they have eight electrons around them. I just now used all the electrons. I don't have any electrons remaining here. We'd say that are central element has what it has three bonding groups. Zero lone pairs. Remember we have three bonding groups and zero lone pairs. Your molecular geometry would be tribunal planner also I could see that it was gonna be triggering a planer beforehand. So that's why I drew it in this way. Remember the visualizations that I provided for each of the shapes. Means you need to draw it that way. So they could really represent the true shape of the molecule. Now, if you don't see it initially go back and readjust your shape to make it look like this. Okay, So it should look something close as possible to the visualization in the videos that I've previously shown. Right? So just remember in this particular case, we're dealing with trivial planner for this particular molecule.

Molecular Geometry (Simplified) Concept 3

Here, we're going to say that central elements with four electron groups can have anywhere from 0-2 long pairs to give us three possible molecular geometries. So here we have four electron groups. And that can translate to having four electron bonding groups and zero lone pairs or three bonding groups in one long pair Or two of each. Realize here when you add up your bonding groups with your lone pairs. Yeah, it should give you back a total of four for the number of electrons groups. Now when we have four Bondi groups and zero lone pairs here we have a good example of CH four. The visual representation is the way you should draw it when illustrating these different types of molecules here. The molecular geometry would be tetra federal For the next one. When it's three bonding groups in one long pair, we have a good example in Ammonia, which is NH three. That one lone pair is up here. If you would've visually represent this, it would look like a pyramid. And that's why the name here is Tribunal Pure Middle Tribunal because it's three corners of this pyramid and pyramid. All because it's a pyramid. Now when it's two and two, this is interesting because when it's two and two, we know that we have long players here which is causing the spending. And there was a long pair up here here. We've seen these terms before. When it's two and two, it's bent V shaped or angular. So if you watch my previous video, you would know that when we drew uh to bonding groups in one lone pair, it also had these same shapes of bent V shaped and angular. So just remember, it also applies when we have to bonding groups and two lone pairs on the central element. Now again, when the more electron groups we have on the central element, the more possible shapes that arise when we have four electron groups. We have these three possible shapes that arise, and for that last one, you could use any of those three names bent, V shaped, or angular. They all mean the same thing.

Molecular Geometry (Simplified) Example 2

determine the molecular geology for the following ion of NH four positive otherwise known as the ammonium ion. So nitrogen is in group five a. So we have five valence electrons, Hydrogen in Group one a. And there's four of them then remember a plus one charge means we've lost an electron. So we subtract this from the total, that means we have eight total valence electrons. Nitrogen will go in the centre because hydrogen can never go in the center, hydrogen only makes single bonds. Yeah, remember each covalin bond that we just drew represents two valence electrons. So we just used all eight of our electrons leaving us with none left because it's an ion we put it in brackets and the charge in the type top right corner. At this point we would say that our central element has connected to it for bonding groups And it has zero lone pairs. Remember when you have four bonding groups and zero lone pairs, your molecular geometry would be tetra head roll. So we say here that your molecular geometry for the ammonium ion is tetra federal. If we wanted to draw it in the correct way with our by our visual representation, it would look closer to something like this. The shape is a little bit weird and jarring when you look at it. So it's ok if you want to draw it as the first option that I drew, and again, you still put it in brackets with the charge in the top right corner.