The ozone ($O_3$) molecule has an angular (bent) structure and is a resonance hybrid of two main canonical forms: $O=O^+-O^-$ and $O^--O^+=O$. In its structure, the central oxygen atom is connected to one terminal oxygen atom by a double bond and to the other by a single bond. Since a single covalent bond consists of one $\sigma$ bond, and a double bond consists of one $\sigma$ and one $\pi$ bond, the $O_3$ molecule contains a total of 2 $\sigma$ bonds and 1 $\pi$ bond.