Linear electron-group arrangement

Figure 10.4 The single molecular shape of the linear electron-group arrangement. The key (bottom) for A, X, and E also refers to Figures 10.5, 10.6, 10.8, and 10.9.

Figure 10.3 The single molecular shape of the linear electron-group arrangement.

For the trigonal bipyramidal shape of the PCI5 molecule, for example, the VB model proposes that the one 35, the three 3p, and one of the five 3d orbitals of the central P atom mix and form five sp d hybrid orbitals, which point to the vertices of a trigonal bipyramid (Figure 11.6). Seesaw, T-shaped, and linear molecules have this electron-group arrangement with lone pairs in one, two, or three of the central atom s sp d orbitals, respectively. 

What type of central-atom orbital hybridization corresponds to eadi electron-group arrangement (a) trigonal planar, (b) octahedral (c) linear, (d) tetrahedral (e) trigonal bipyramidal ... 

Because each of acetylene s central atoms has two electron groups around it, the arrangement of atoms around each is linear. Figure 12.10 shows four ways to describe a C2fl2 rnolecule. 

Linear geometry The geometric arrangement that keeps two electron groups as far apart as possible. It leads to angles of 180° between the groups. 

The Molecular Shape with Two Electron Groups (Linear Arrangement)... 

When two electron groups attached to a central atom are oriented as far apart as possible, they point in opposite directions. The linear arrangement of electron groups results in a molecule with a linear shape and a bond angle of 180°. Figure 10.4 shows the general form (top) and shape (middle) with VSEPR shape class (AXa), and the formulas of some linear molecules. 

For instance, two electron groups are most stable on opposite sides of the central atom (the linear arrangement), where they repel one another as little as possible. Three regions are most stable when they are arranged at the corners of an equilateral triangle. Table 8-1... 

You have two double bonds, or two electron groups, about the carbon atom, and these are treated as though there were two pairs on carbon. Thus, according to the VSEPR model, the bonds are arranged linearly and the geometry of carbon dioxide is linear. 

Qualitative models of reactivity and quantum mechanical calculations of reaction paths both indicate an angular approach of the attacking nucleophile to the first-row sp -hybridized electrophilic centers M at intermediate and reactive distances, 29. The geometry of 29 is also characteristic for the case of nucleophilic addition to electron-deficient centers of main-group 12 and 13 elements. By contrast, a linear arrangement 30 of making and breaking bonds is required for sp -hybridized first-row centers (C, N, O)... 

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