The Foundations of Chemistry

8-3 Polar Molecules: The Influence of Molecular Geometry 311

TABLE 8-1 Number of Regions of High Electron Density About a Central Atom

No. Regions

Electronic Geometry*

of High Electron Description;
Density Angles† Line Drawing‡ Stereo View§

2 linear;

180°

3 trigonal planar;

120°

4 tetrahedral;

109.5°

5 trigonal bipyramidal;

90°, 120°, 180°

6 octahedral;

90°, 180°

*Electronic geometries are illustrated here using only single pairs of electrons as regions of high electron density. Each orange sphere represents a region of high elec-
tron density about the central atom (gray sphere).Each may represent either an atom bonded to the central atom or a lone pair on the central atom.
†Angles made by imaginary lines through the nucleus and the centers of regions of high electron density.
‡By convention, a line in the plane of the drawing is represented by a solid line XX, a line behind this plane is shown as a dashed line ,,, and a line in front of
this plane is shown as a wedge !with the fat end of the wedge nearest the viewer.
§View the three-dimensional drawings with the aid of the viewer inside the cover of the text.