Axial position
Definition
Axial position refers to the positions along the axis of a trigonal bipyramidal molecular geometry, typically occupied by atoms or groups. These positions are aligned perpendicular to the plane containing the equatorial positions.
5 Must Know Facts For Your Next Test
- In a trigonal bipyramidal molecular geometry, there are two axial positions and three equatorial positions.
- Atoms in axial positions experience more repulsion compared to those in equatorial positions due to 90° bond angles with three other atoms.
- Axial bonds are generally longer than equatorial bonds due to increased repulsion forces.
- Substituents prefer equatorial positions over axial when possible because of lower steric hindrance and electron repulsion.
- An example of a molecule with distinct axial and equatorial positions is phosphorus pentachloride (PCl$_5$).
Review Questions
- How many axial and equatorial positions are present in a trigonal bipyramidal structure?
- Why do atoms in axial positions experience more repulsion compared to those in equatorial positions?
- Provide an example of a molecule that exhibits both axial and equatorial positions.
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Related terms
Equatorial Position: Positions in a trigonal bipyramidal structure that lie in the same plane, usually associated with lower steric hindrance.
Trigonal Bipyramidal: $AX_5$ molecular geometry with three atoms forming an equilateral triangle (equatorial) and two atoms positioned axially.
$PCl_5$: $Phosphorus pentachloride$, a compound that adopts a trigonal bipyramidal structure at room temperature.
