chemical compoundsmoleculesorbitalsphysical-chemistrywater
When you see models of water you see something like this:
The hydrogens in the water molecule become negatively charged because the oxygen pulls electrons more. So why don't they repel and move to the opposite sides of the oxygen? Or just form on opposite sides in the first place?
The difference between rain and water in the sink is that rain is simply falling, while water in the sink is being drawn into a center from a distance away, and the water in the sink is not perfectly still. It is rotating, if only a little bit. As it is drawn to the center, the rotation becomes more rapid.
The principle is Conservation of Angular Momentum.
Here, Ms. Kawaguti speeds up her rotation by pulling in her arms:
As part of an undergraduate project I calculated the electron density for various small molecules such as water and ammonia, and the disappointing result is that they are all basically formless blobs with only small bumps where the hydrogen atoms are. They ended up looking much like your last picture of water:
though even that picture exaggerates the bump in the electron density caused by the hydrogen atoms. Sadly I no longer have the results from my calculations, but then they were done in 1983.
So if you could see the water molecule I'm afraid it would just look like a roughly spherical fuzzy blob.
Best Answer
There are six electrons in the outer orbital of an oxygen atom. In a water molecule two of these electrons bond with the lone electron of each hydrogen atom to form two “bond pairs”. The remaining four oxygen electrons pair up to form two “lone pairs” (because of quantum mechanics, it is energetically favourable for electrons with opposite spins to form pairs).
If the repulsive forces between the bond pairs and the lone pairs were completely symmetrical then the four pairs would form the vertices of a regular tetrahedron, and the angle between the hydrogen atoms (the “bond angle”) would be approximately 109 degrees (the exact angle is $\cos^{-1}\left(-\tfrac 1 3 \right)$). This is what happens when four hydrogen atoms and one carbon atom form a molecule of methane, which has four bond pairs.
However, in water the repulsive forces are not quite symmetrical and the hydrogen atoms are pushed a bit closer together - the actual bond angle is about 104 degrees.
See this Wikipedia article for more details.