axial/equatorial

[705340227]

Can someone explain what the axial and equatorial positions mean and how to determine which one a region of electron density is?

[Anh Trinh 1J]

An axial lone pair lies on the axis of the molecule, where it strongly repels the electron pairs, and lie at 90 degree angles to the axial position. An equatorial lone pair lies on the molecule's equator, on the plane perpendicular to the molecular axis.

For example, in a trigonal bipyramidal, an equatorial position is preferred because a lone pair is close to only two atoms, as compared to the axial position where it is close to three atoms. You want to lower the repulsion by having the bonding pairs move away from the lone pair. You can determine by drawing the Lewis structure and find which position that the lone pairs are as far from one another and from bonding pairs as possible; the lowest energy is achieved when lone pairs are as farthest from each other.

[Hayden Lee 1C]

An atom in an axial position is perpendicular to the plane of the "ring," or the atoms that lie in the plane with the central atom. Atoms in equatorial positions are around this plane of the ring and are perpendicular to the axial atoms.

[Daniela Santana 2L]

The way I think about this is by envisioning a globe. I know that the globe's equator cuts across the middle of it horizontally so the equatorial position must be the atoms that are attached to the sides of the central atom. The globe's axis starts from the top of the globe and cuts its way down to the bottom of the globe in a vertical way, so the axial position must be the atoms that are attached to the top and bottom of the central atom. I hope this helped!

[jasmineculilap_3F]

Equatorial are on the same horizontal plane as the central atom while axial are above/below that plane.

[Chenning Yang Dis3l]

Thank you for the info!