Why does the H2O molecule have a bent shape instead of a straight shape?

The water molecule ($H_{2}O$) is not linear because of its specific electronic structure, which includes two bonding pairs and two nonbonding pairs of electrons (lone pairs) around the central oxygen atom.12

The oxygen atom has six electrons in its valence shell, and when it bonds with two hydrogen atoms, it completes its shell with eight electrons. These electrons arrange themselves in a tetrahedral geometry, with the oxygen nucleus at the center. Two of the four "legs" of this tetrahedron are occupied by the hydrogen atoms (bonding orbitals), while the other two are occupied by the lone pairs of electrons.12

Because these lone pairs exert a repulsive force, they influence the positioning of the hydrogen atoms, resulting in a bent molecular shape with a bond angle of approximately 104.5° to 105°. This bent structure is fundamental to the polarity of the molecule and its ability to form hydrogen bonds, which are responsible for many of water's unique physical and chemical properties. While VSEPR theory is often used to explain this geometry through electrostatic repulsion, it remains a simplified model for understanding complex molecular interactions.123