I not get molecular shapes- could someone please tell me the central idea and pattern . I know that lone pairs and the number of bonds affect the shape, but I feel that I still don't get the main idea.

Question

I not get molecular shapes- could someone please tell me the central idea and pattern . I know that lone pairs and the number of bonds affect the shape,  but I feel that I still don't get the main idea.

jfraser · Answer

molecular shapes are all about the electrons trying to get as far away from each other as possible. this repulsion of electrons creates different shapes depending on how many "domains" a molecule has. Proper Lewis structures are a must for knowing molecular shapes.  In the picture, the balloons represent areas of electron density, or "domains". The electrons could be bonded pairs, or they could be lone pairs. With me so far?

anonymous · Answer

Yes, I'm with you so far.

jfraser · Answer

a molecule like CO2 has 2 domains, since the central carbon has only 2 double bonds connecting the oxygens. The maximum separation of these bonds is 180degrees, so the CO2 molecule is linear. The nitrate ion has 3 domains, since the central nitrogen has 3 bonds connecting its oxygens, so the nitrate ion is trigonal planar. more domains means more complicated shapes, but it all boils down to getting a lewis structure