CHAPTER 1 Stereochemistry and Bonding in Main Group Compounds: 17 electron-pair domains is trigonal bipyramidal with equatorial and axial bond angles of 120° and 180°, respectively; in this case, the non-bonding domain would require more space than the bonding domains. Now the question arises here is what position this non-bonding electron-pair domain should occupy in a trigonal- bipyramidal frame. After seeing that each axial position has three neighbors at 90° while every equatorial position has only two 90° neighbors, we can conclude that the equatorial position is more suitable for the placement of lone pair.
This, in turn, would result in a greater lone-pair–bond-pair repulsion yielding the distortion of a perfect seesaw-shaped derivative with axial and equatorial bond angles slightly less than their normal of 180° and 120°. Figure 11. Structure of SF 4 molecule from the VSEPR model. iii) ClF 3 : The central atom in ClF 3 molecule is Cl which has seven valence electrons (2, 8, 7). Now because each fluorine atom needs one electron to complete its octet (2, 7), the Cl atom uses its three valence electrons to create three bond pair domains, while four electrons are left as two lone pair domain.
Now though the geometry for five electron pair domains is trigonal bipyramidal equatorial and axial bond angles of 120° and 180°, respectively; but in this case, the non-bonding domain would require more space than the bonding domains, and therefore need to be placed on the equatorial position. This, in turn, would result in greater lone- pair–lone-pair repulsion yielding the distortion of perfect T-shaped derivative with axial equatorial bond angles less than their normal of 180°. Figure 12. Structure of ClF 3 molecule from the VSEPR model. Buy the complete book with TOC navigation, high resolution images and no watermark. Copyright © Mandeep Dalal