Question

What is the bond angle in a water molecule?

Answer 1

`104.4776^@`

You can derive the approximate angle by knowing that the oxygen in water has four electron groups, giving it a tetrahedral electron geometry, and a bent molecular geometry.

From knowing that it has a tetrahedral electron geometry, but two lone pairs of electrons, one question should pop into your mind:

"Why does water not have a `109.5^@` H-O-H bond angle? "

It's because the two nonbonding `2p` orbitals on oxygen impose a spatial repulsion, bending together the two hydrogens and decreasing the bond angle, which is measured such that it is `<=180^@`.

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(It is acceptable to just say `104.5^@`, but it is known to more decimal places than just one.)