Understanding Bent's Rule

Bent's rule provides a model to predict the hybridization of a central atom in a molecule, particularly concerning the distribution of $s$ and $p$ character in hybrid orbitals.

Applying Bent's Rule to Substituent Position

The rule states that hybrid orbitals with higher $p$ character are directed towards more electronegative substituents, while orbitals with higher $s$ character are directed towards more electropositive substituents.

Geometry and Electronegativity Preference

For elements in the $p$-block, consider the trigonal bipyramidal geometry:

• This geometry has distinct positions: three equatorial and two axial.
• The hybrid orbitals involved typically have slightly more $p$ character in the axial direction compared to the equatorial direction.
• Consequently, more electronegative substituents preferentially occupy the positions with higher $p$ character.

Therefore, in a trigonal bipyramidal arrangement, more electronegative substituents will occupy the axial positions.

Conclusion for $p$-block Elements

Based on Bent's rule, for $p$-block elements exhibiting a trigonal bipyramidal geometry, the correct combination is that more electronegative substituents are found in the axial positions.