![]() When, however, one or more domains involve nonbonding pairs of electrons, we must remember to ignore those domains when talking about molecular shape. ![]() When all the electron domains in a molecule arise from bonds, the molecular geometry is identical to the electron-domain geometry. From knowing how many of the domains are due to nonbonding pairs, we can then predict the molecular geometry. In determining the shape of any molecule, we first use the VSEPR model to predict the electron-domain geometry. In contrast, the molecular geometry is the arrangement of only the atoms in a molecule or ion-any nonbonding pairs in the molecule are not part of the description of the molecular geometry. The arrangement of electron domains about the central atom of an AB n molecule or ion is called its electron-domain geometry. The shapes of different AB n molecules or ions depend on the number of electron domains surrounding the central atom. If you compare the geometries in Table 9.1 with those in Figure 9.3, you will see that they are the same. These arrangements, together with those for five- and six-electron domains, are summarized in TABLE 9.1. Like the balloons in Figure 9.5, two electron domains orient linearly, three domains orient in a trigonal-planar fashion, and four orient tetrahedrally. In fact, the analogy between electron domains and balloons is so close that the same preferred geometries are found in both cases. The best arrangement of a given number of electron domains is the one that minimizes the repulsions among them. Like the balloons in Figure 9.5, electron domains try to stay out of one another's way. The VSEPR model is based on the idea that electron domains are negatively charged and therefore repel one another.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |