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Electron Domain And Molecular Geometry

In chemistry and physics, the molecular geometry describes the geometric arrangement of the atoms that form a molecule. It is determined by the nature of the chemical bonds between the atoms. These constraints result in the molecule adopting a regular geometric form, like a polyhedron or a sphere. The molecular geometry can be determined by various spectroscopic methods and diffraction methods.


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Video Transcript

So now that we know how to again right the blue structures and determine the regions of funding as well as the region's with parents, we can go ahead and assign the geometry based on the number of bonds. And then we can adjust the geometry at the little Paris, are present on the central atom and then reassigned the geometry. And so let's write this out on the side. So if you remember, and so that third step will be assigning geometry, looking at the bonds. And so if we look at the first problem, we have a molecule with four bonds and so we know that there's zero electrons and in this case we need to maximize the angles of all of the items because we know that the electrons for each of these items will be repelling each other. And so it is most stable when they are farther away from each other, and so we can see that we have four runs and so we can assign this as the Tetra Hydro, which basically looks like this. So we have boron and the floor Eanes, and this has a negative charge and the angles are such that the atoms for 109.5 degrees away from each other. And so because we don't have any loan Paris, we don't need to adjust the geometry for the specific molecule. And now, if we go into our next example, we have a case where we have a molecule three bones and I don't have enough space here. Eso I'm just going to write this on the left side. And so we have We're on, and we can see that we don't have any lone pairs. And if you want Thio, maximize the angles between all of the items, the angles should be 120 degrees. We can draw the geometry like so, and we can assign this as the tricking all cleaner because that all of these atoms are in one plane and there are through and again we don't have any mill in pairs, so we don't need to worry about the distortion in the geometry. And so in this case we are. And if we look at water, we see that we have to bonds and we have to lone pairs. So if there were no lump hairs, this would simply be a linear molecule. But because there are low in Paris, this will actually distort the geometry. And so far, last step. We need Thio, adjust the geometry. If we have loan Paris that exists. And so in this case we do. And so we need to adjust the one year on DSO We know that the loan Paris will actually push the bonds closer to each other. And so this would actually result in a bend structure which we already drew here. But I'll just draw it again. And so we have to love pears that are pushing the hydrogen is toward each other. And so this bond angle would be less than 109.5 degrees. And so this would be a band structure. And now, for our last molecule, we have a nitrogen that is triply bound to another nitrogen. And so in this case we only have one area with electrons, which is the bond between the two nitrogen. And so this is actually just a linear structure where the angle between two atoms are 1 80 degrees. And so in this case, we again have a linear structure because this optimizes the angle between the two atoms because of propulsion. And so this is how you would assign the geometry. And so whenever we use thievy S e p R model, we need to make sure that we know how to write the Louis structure of the molecule. And then from there we can determine the regions of bonding and lone pairs with respect to the central atoms. And then, from there, we can use the molecular geometries that we've learned before to assign the correct one based on the number of bonds. And then from there, we can also consider the lone pairs to see how we can adjust the geometry, because the lone pairs introduce the distortions.