Molecular Geometry

the molecular geometry of a compound can be seen as the true shape of that molecule compound. That takes into account differences and repulsion between lone pairs and surrounding elements. Now, because of this we would treat lone pairs on the central element and surrounding elements as different. So they're not going to be treated as the same. Now, we're going to take a look at each of the number of electron groups that exist. Starting out with two electron groups. Now, when we have two electron groups are going to say here, this is central elements with two electron groups that have zero lone pairs and give only one possible molecular geometry. So if we take a look here, We have two electron groups, we say that there are zero lone pairs. So that means we're gonna have to bonding groups possible. Remember bonding groups are just your surrounding elements. Zero lone pairs here are some examples in all of them. We have a central element here. We have beryllium, carbon and carbon again, and they are connected to only two surrounding elements. Now it doesn't matter if it's single bonded to them or double bonded or triple bonded, it's still too surrounding elements or two bonding groups visually would see it as our black spear here, which is our central element connected to those gray spheres which are surrounding elements here. The molecular geometry for all of them would be linear. So when it comes to two electron groups around the central element, there's only one possible molecular geometry and that's a linear molecular geometry

when it comes to three electron groups were going to say this is when central elements with three electron groups that can have either zero or one lone pair to get to possible molecular geometries. So again, when we have three electron groups around our central element to possible shapes can occur. So we have three electron groups. In the first situation we have three surrounding elements or three bonding groups and zero lone pairs. Here we have an example of carbon in the center connected to three surrounding elements. It's visualization would look like this and we'd say that its molecular geometry will be tribunal player. Now, another option that could occur is we have to surrounding elements or two bonding groups and one lone pair on the central element here we have our example with tin in the center with two chlorine and it has one lone pair in its visualization, we have lost the element that was here and it's been replaced by a long pair. Now remember lone pairs have an electron cloud which further causes more repulsion. So that's why it looks kind of like that. And it's shaped kind of fits the name here. We'd say that its molecular shape is bent. You might also see the name V shaped or you might even see the name angular. So just remember all of these names are synonymous for the same thing. They're talking about a molecular structure in this case where we have to surrounding elements and one lone pair in terms of this one and other ones like it. Right. So keep in mind when you have three electron groups around your central element to possible molecular geometries are possible.

determine the molecular geometry for the following. And I on here we have beryllium connected to three hydrogen. Is and there's a negative charge. Now, beryllium itself is a group to weigh and we're going to say because of that it has two valence electrons. But here we have three hydrogen. So we would need three valence electrons. That's gonna be okay because this minus one charge means we gained an electron from the outside. So we add an additional electron to beryllium. Remember hydrogen only have one valence electron since their in group one a and they only make single bonds because this has a charge we put in brackets and the charge on the outside. Now, if we take a look here, we'd say that beryllium is connected to three electron groups, three surrounding hydrogen. It has no lone pairs on it. So we have three Electron groups zero lone pairs. And because of that, our molecular geometry would be tribunal plan. So this would be the molecular geometry of our particular and I'll

Central elements with four electron groups can have either zero one or two lone pairs to give three possible molecular geometries. So we take a look here, we have four electron groups. And the way we can split this up is our central element could have four surrounding elements and no lone pairs. You could have three surrounding elements and one lone pair. Or could have to surrounding elements in two lone pairs. If we take a look here, we have different examples of shapes that fit this criteria. Here we have Ch four, which is methane. Here we have ammonia, which is NH three. And here we have water. They're visualizations. We have carbon in the center with its four hydrogen attached to it. Now here for nitrogen we have our three surrounding elements and on top we have our lone pair. Remember lone pairs have their own electron cloud which caused further repulsion. Water here would have to long pairs on the oxygen which causes further propulsion. Now here, what would the names of the geometries? B Well, here, if we have four surrounding elements and no long pairs, it would be called tetra federal for the next one, it kind of looks like a pyramid. A pyramid with three legs. So that's why we call it tribunal here a middle and then finally water. We have two long pairs on the central element into surrounding groups here. It kind of looks familiar to us. We saw a shape similar to this when we talked about two electron groups. We'd say that this looks bent or v shaped or angular. Now any one of these three terms could be used to identify this particular shapes or treat them all as the same. So just remember when we have four electron groups, there are three possible molecular geometries that are possible.

Central elements with five electron groups can have 20 to 3 lone pairs to give four possible molecular geometries. So we can have 012 or three lone pairs on our central element. So here we have five electron groups. And the way it can break down is we have five surrounding elements or bonding groups and zero lone pairs on the central element. Or it could be 4-1 Or it could be 3 - two. Or finally it can be 2 - three. Now, here, if we take a look, we have examples here, we have phosphorus Penta chloride here we have selenium tetrachloride. Here we have bro mean bro mean tri iodide and here we have zen in decline as examples. Now they're visualizations here. If we take a look visually, this would look like two pyramids that are stacked on top of each other. And if we think about it's 23 legged pyramids stacked on top of each other. It's molecular geometry. Name would be tribunal because each pyramid has three legs and there's two pyramids on top of each other by pyramidal. For the next one. If we have four surrounding elements and one lone pair on the central element, it would visually look like this here. I've added a person here and a person here to help us think of what this would look like in a daily object. So if you look at it, it kind of looks like a seesaw. So that's the name seesaw. Mhm. For the next one, If you have three surrounding elements and two lone pairs on your central element, this here looks like the letter T. So that's what we call it, T shaped. And then finally, if you have to surrounding elements and three lone pairs on your central element, you look linear, like a straight line. So these would be our different possible molecular geometries if we have five electron groups involved in our molecule. Alright, so keep them in mind and just remember visually what they look like. That's a great way to help you remember their name.

draw and determine the molecular geometry for the following molecule sl cl four. So here sulfur would go in the center, It's in group six a. So it has six valence electrons, Halogen slows and elements in group seven a. Only makes single bonds when they are surrounding element. So sulfur is gonna single bond to four of the chlorine, the chlorine, our in group 78. So they have seven valence electrons. So here they go here now remember sulfur can have an expanded octet, which means I'm gonna have more than eight electrons around it and I'll have to in order to incorporate the oxygen, oxygen ideally wants to make two bonds, sulfur can expand its octet so soft is gonna help it out and make a double bond to the oxygen oxygen is in Group six is what has six valence electrons. So here this would be the shape of our sl cl for structure and we're going to say it is connected to five bonding groups or surrounding elements and has no lone pairs on it. So it would be tribunal by pyramidal. It's okay, so this would represent its molecular geometry

Central elements with six electron groups can have 0-2 lone pairs to give three possible molecular geometries. So if we have six electron groups, the combinations that exist are we can have six bonding groups which are surrounding elements and zero lone pairs. Or we could have five surrounding elements and one long pair. Or we could have four surrounding elements in two lone pairs on the central element. Here we have some good examples of this here. We have sulfur hexafluoride. Here we have chlorine, peta bromide. And then here we have xenon tetrachloride. Now they're visualizations for sulfur. Tech hex on fluoride. We have sulfur in the Senate with its six um surrounding elements, six surrounding florins. Here the molecular geometry would be Octa federal for the next one, we have chlorine, Penta bromine. And if we're to visually show it, we can see that it looks like a pyramid and this pyramid has a base that's square shaped. So that's why it's name is square pyramidal. So just remember if you have a central element that has five surrounding elements in one lone pair, it's square pyramidal. Then finally, the last one here, we have four surrounding elements and two lone pairs here, it would take on a square shape. And here it's on a flat plane. So that's why this is called square planer or square planet. So these are the three molecular geometries that exists. If you're dealing with six electron groups on your central element

determine the molecular geometry for the following ion. So here we have um Krypton Penta chloride cat eye on. So krypton is in group a day. So it has eight valence electrons, but plus one means we've lost one electron. So now it only has seven, we're going to say here the chlorine, it's gonna single bond to them. And here we're gonna have a long pair on the bottom. The Chlorine is in group 7 8. So they have seven valence electrons. So when we draw this out we can see that our krypton has around it five surrounding elements or five bonding groups. And it has one long pair. Remember when we have this type of situation, we'd say that this is square, pure middle. So this would represent the molecular geometry of krypton Penta chloride cat island.