Shape vs. Geometry

[kiara chan]

I'm a little confused on the difference between the shape vs. geometry of a compound, can someone explain please? thank you!

[Natalie Keung 1D]

Electronic geometry is the shape that relates to the amount of regions of electron density. This would be trigonal planar (3 regions of e density), tetrahedral (4 regions of e density), trigonal bipyramidal (5 regions of e density), and octahedral (6 regions of e density). Under each category of electronic geometry, there are shapes that are formed from the replacement of an atom with a lone pair. For example, for a tetrahedral electron geometry, there are 3 options of shape, tetrahedral (no lone pairs), trigonal pyramidal (one lone pair), and bent (two lone pairs). I hope this helps.

[Jessica Phung 1E]

The geometry is also referred to as electron arrangement and this might help you differentiate. For example, the electron arrangement has to do with all the electrons surrounding the center atom, including lone pairs (so, regions of electron density). The shape only has to do with the bonds and atoms attached to the center atom, BUT you still have to consider the influence of the lone pairs. Which is why for water, the electron arrangement would be tetrahedral but the molecular shape is bent.