# What is the bond angle in a water molecule?

Nov 15, 2015

${104.4776}^{\circ}$

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 ${109.5}^{\circ}$ H-O-H bond angle? "

It's because the two nonbonding $2 p$ orbitals on oxygen impose a spatial repulsion, bending together the two hydrogens and decreasing the bond angle, which is measured such that it is $\le {180}^{\circ}$.

(It is acceptable to just say ${104.5}^{\circ}$, but it is known to more decimal places than just one.)