The ozone formation is endothermic and requires heat. ... But in case of ozone, there is one more oxygen atom. The third oxygen atom pushes one of its lone pairs of electrons toward one of the double bonded oxygen atoms. Thus, it interrupts the overall structural stability and thus, the molecule becomes unstable.

How is ozone unstable?

Ozone (O₃) is a molecule composed of three oxygen atoms, in contrast to ordinary oxygen (O₂), which has only two oxygen atoms. Because of its atomic structure, ozone is an unstable gas that quickly decomposes into ordinary oxygen, especially in water.

Is O3 stable or unstable?

Ozone (O3) is a relatively unstable molecule made up of three atoms of oxygen (O).