VSEPR model trigonal pyramidal

Valence shell electron pair repulsion (VSEPR) model Trigonal pyramid... 

SOLUTION The Lewis structure of nitrogen trifluoride is shown in (22) we see that the central N atom has four electron pairs. According to the VSEPR model, these four electron-rich regions adopt a tetrahedral arrangement. Because one of the pairs is a lone pair, the molecule is expected to be trigonal pyramidal (23). Spectroscopic measurements confirm this prediction. 

Fig. 5. Geometries detected by TAMREAC according to the Angular Overlap and VSEPR models for four- and five-coordinate complexes. Abbreviations SPL = square planar, Td = tetrahedral, SPY = square pyramidal, TBP = trigonal bipyramidal, Is = low spin, hs = high spin, d" = number of electrons in the d configuration of the metal.

The structures of the element trihalides EX3 are covered in a number of textbooks on structural inorganic chemistry (4, 5), and these will not be discussed in great detail here. It is, however, worth mentioning some of the salient structural features. In most cases, a molecular trigonal pyramidal EX3 unit consistent with VSEPR theory predictions is readily apparent in the solid-state structure, although there are usually a number of fairly short intermolecular contacts or secondary bonds present. A general description of the structures as molecularly covalent but as having a tendency toward macromolecular or polymeric networks is therefore reasonable. Only in the case of the fluorides is an ionic model appropriate. 

The amended VSEPR model predicts two forms of five-coordination, and experimental chemistry has clearly identified many examples of both forms. These limiting structures are square-based pyramidal (or, simply, square pyramidal) and trigonal bipyramidal (Figure 4.13). The classical square-based pyramidal shape is formed simply by cleaving off one bond from an octahedral shape, which leaves the metal in the same plane as the four square-based ligands. In reality, almost no complexes exhibit this shape, but rather adopt a distorted... 

PCI3 is trigonal pyramidal (use the VSEPR model) and so possesses the same symmetry elements as NH3 in worked example 4.2. These are E, C3 and 3cfy. 

Show that the tetrahedral and trigonal pyramidal Sb centres in cation 19.56 are consistent with the VSEPR model. Comment on what this assumes about the localization of the positive charge. 

Section 8.13 molecular structure valence shell electron-pair repulsion (VSEPR) model linear structure trigonal planar structure tetrahedral structure trigonal pyramid trigonal bipyramid octahedral structure square planar structure... 

The VSEPR model is used to determine molecular shape. It assumes arrangements that minimize repulsion of electron pairs around the central atom. The presence of four bonding pairs produces a tetrahedral arrangement. Three such pairs produce a trigonal planar shape, unless there also is a lone pair on the central atom, in which case the shape is trigonal pyramidal. Two bonding pairs produce a linear shape, but if there also are two lone pairs on the central atom, the shape will be bent. 

---