Molecular Geometry Concept 3

by Jules Bruno
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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.