What are the electron geometry and the molecular geometry of water?

1 Answer
Jul 17, 2016

The electronic geometry gives water a tetrahedral shape.
The molecular geometry gives water a bent shape.


Electronic geometry takes into account the electron pairs that are not participating in bonding, and the electron cloud density.

Here the 2 bonds of hydrogen count as 2 electron clouds, and the 2 electron pairs count as another 2, giving us a total of 4. With 4 electron regions, the VSEPR electronic geometry is tetrahedral.


Molecular geometry looks at only those electrons that are participating in bonding. So here, only the 2 bonds to H are taken into account.

The shape would not be linear, as in the case with #"CO"_2#, even though there are only 2 bonds in #"H"_2"O"# due to the fact that the unpaired electrons would not allow such a shape.

There is electron repulsion going on so electrons take on shapes that help to reduce electron repulsion.