Molecular shapes?

Question

Why is it that water holds the H- molecules down at an angle like a triangle while CO2 holds the O2 at 180 degrees from one another with the carbon in the middle??

Answer 1

The O of water is sp3-hybridized. That means that the bonds to H's or to nonbonding electrons are 108deg. There is no triangle, but a tripod. The O stands on a tripod of three H's. The two pair of nonbonding electrons stick up in the air: **. The nonbonding electrons take up the "room" that would be occupied by other atoms.

By contrast, the C of CO2 is sp hybridized. That means that the C=O bond sticks out in one direction and the other C=O in the other. The bond angle is 180deg.