Question

In a trigonal bipyramidal electron domain geometry (total electron domain number = 4), where is the lone pair predicted to be found?

1) Axial
2) Equatorial

Answer 1

In trigonal bipyramidal electron domain geometry, lone pairs are predicted to be found in equatorial positions to minimize electron pair repulsion and maximize stability.

Step-by-step explanation:

In trigonal bipyramidal electron domain geometry, which refers to a molecule with a total of five electron pairs around a central atom, there are two possible positions for electron pairs: axial or equatorial. According to Valence Shell Electron Pair Repulsion (VSEPR) theory, lone pairs occupy positions where they can minimize electron-pair repulsion. As such, lone pairs are preferably found in the equatorial positions due to the larger 120° bond angles which offer more space compared to the 90° bond angles experienced at the axial positions. This arrangement minimizes the electron repulsion and leads to a more stable molecule. For example, in a molecule like SF4 (AX4E), the lone pair occupies an equatorial position, resulting in a seesaw-shaped molecular structure.