Final answer:
Water is bent because it has two bonded pairs and two lone pairs of electrons around the central oxygen atom which creates repulsion, that pushes the hydrogen atoms closer, forming a bent molecular structure.
Step-by-step explanation:
Water has a bent molecular structure because it has four electron groups around the central oxygen atom. Specifically, there are two lone pairs of electrons and two bonded pairs of electrons (which form the bonds with hydrogen atoms). While the electron groups are oriented in the tetrahedral shape, the presence of the lone pairs leads to a repulsion that pushes the bonded hydrogen atoms together, creating a bent shape with an angle slightly less than the 109.5° expected in a regular tetrahedral structure. In water, the H-O-H bond angle is approximately 104.5° as a result of this lone pair repulsion.