[kentucky_girl]

Hi all, I'm just trying to work on some test review problems, and I'm a little confused about what they're asking.

Here are the instructions: Give the electron-domain and molecular geometries for the following molecules and ions.

It gives you the choices of:
Bent
Linear
Octahedral
Seesaw
Square planar
Square pyramidal
Tetrahedral
Trigonal planar
Trigonal pyramidal
Trigonal bipyramidal


I don't understand how to find the electron domain, or what that's talking about. I'm pretty sure I have the molecular geometry down, but correct me if I'm wrong.

CO32-
electron domain: ?
molecular geometry: trigonal planar

TeF4
electron domain:
molecular geometry: trigonal bipyramidal

NH3
electron domain:?
molecular geometry: trigonal pyramidal

SeCl2
electron domain: ?
molecular geometry: seesaw
XeF4
electron domain:?
molecular geometry: square planar

SF6
electron domain:?
molecular geometry: octahedral

THANK YOU IN ADVANCE!

[Yggdrasil]

The electron domain geometry takes into account the positions of the lone pairs (an electron domain is a chemical bond or a lone pair).  So, for example, the atoms of NH₃ are arranged in a trigonal pyrimidal fashion, but the electron domains are arranged tetrahedrally.

The electron domain geometry essentially amounts to giving the hybridization of the atom.  For example, sp³ hybridized molecules always have a tetrahedral electron domain geometry.