## equatorial v. axial

(Polar molecules, Non-polar molecules, etc.)

josmit_1D
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

### equatorial v. axial

why does lone pair position matter when they are equatorial and not axial?

Daniel Chen 2L
Posts: 101
Joined: Fri Aug 30, 2019 12:15 am

### Re: equatorial v. axial

The repulsion forces and bond angles are different for equatorial and axial. Axial has two repulsion forces since it's two ends of an axis. Equatorial may have 3 or more repulsion forces.

ShreyaKannan1B
Posts: 51
Joined: Wed Sep 11, 2019 12:15 am

### Re: equatorial v. axial

What do equatorial and axial mean?

Ashley Wang 4G
Posts: 103
Joined: Wed Sep 11, 2019 12:16 am

### Re: equatorial v. axial

If I'm understanding your question correctly (why it matters where the lone pair is located on the central atom?), it depends on the molecule.

For example, in an AX4E molecule, the electron arrangement achieves the lowest repulsion if the lone pair is equatorial, because then it only strongly repels the electron pairs in the two axial bonds (as opposed to three equatorial bonds if it were axial).

However, in an AX4E2 molecule, it is more favorable for the lone pairs to be axial, on opposite sides of the central atom, which makes them the furthest apart.

I hope this helped!

Ashley Wang 4G
Posts: 103
Joined: Wed Sep 11, 2019 12:16 am

### Re: equatorial v. axial

ShreyaKannan1B wrote:What do equatorial and axial mean?

In structures where regions of electron density form a "plane" around the central atom with more regions above and below it (such as seesaw, square planar, etc),
- the axial lone pair would be one lying on the "axis" of the molecule, so above and below the "plane", and
- the equatorial lone pair would lie on the "equator" of the molecule, in one of the positions that make up the plane.

I hope this helped a bit!