Question

Select all the statements that correctly explain why lone pairs prefer to occupy equatorial positions in a system with five electron domains.

a A larger bond angle leads to more electron repulsion.
b Alone pair in an axial position will be too far away from the other electron pairs.
c There is less repulsion between electron domains in equatorial positions.
d Alone pair in an equatorial position has more space.

Answer 1

Lone pairs prefer equatorial positions in trigonal bipyramidal structures because these positions offer less repulsion and more space for the larger electron domains of lone pairs, reducing electron-pair repulsions and creating a more stable structure.

Step-by-step explanation:

When considering the placement of lone pairs in a molecule with a trigonal bipyramidal electron-pair geometry, such as the AX4E system in SF4, it is important to understand the spatial arrangement and repulsions involved. Lone pairs prefer to occupy equatorial positions because:

• There is less repulsion between electron domains in equatorial positions due to larger 120° bond angles compared to the 90° angles when lone pairs are in axial positions.
• A lone pair in an equatorial position provides more space for the lone pair which occupies a larger region than a bonding pair, minimizing the electron domain repulsions.
• Electron-pair repulsions are minimized when lone pairs are arranged on the equatorial plane because this configuration leads to fewer instances of 90° LP-BP repulsions, creating a more stable molecular structure.