Ozone (O₃) is a molecule that consists of three oxygen atoms. Despite having available electrons, ozone forms only one double bond. This is due to the concept of resonance and the stability it provides to the molecule.
In ozone, the central oxygen atom is bonded to the other two oxygen atoms. One of these bonds is a double bond, and the other is a single bond. However, the double bond is not fixed between a specific pair of oxygen atoms. Instead, it resonates between the two possible positions. This means that the double bond can be considered to be shared between the two outer oxygen atoms.
The resonance structure of ozone helps to distribute the electron density more evenly across the molecule, which increases its stability. If ozone were to form two double bonds, it would disrupt this resonance and make the molecule less stable.
Additionally, the formation of double bonds is influenced by the octet rule, which states that atoms tend to form bonds until they have eight electrons in their valence shell. In ozone, each oxygen atom achieves a stable octet through the combination of single and double bonds, along with lone pairs of electrons.
In summary, ozone has only one double bond because the resonance structure it forms provides greater stability to the molecule. The octet rule also plays a role in determining the number of double bonds, ensuring that each oxygen atom achieves a stable electron configuration.