How many number of $\mathrm{S}-\mathrm{S}$ bonds are there in Sulphur trioxide trimer (${\mathrm{S}}_3{\mathrm{O}}_9$)?

Sulphur trioxide trimer (${\mathrm{S}}_3{\mathrm{O}}_9$):-

• Trimer is defined as the combination of three same compounds(monomer).
• It is a trimer of Sulphur trioxide(${\mathrm{SO}}_3$).
• The structural formula for Sulphur trioxide trimer is

• In this compound Sulphur has $+6$ oxidation state.
• There are total $18\mathrm{S}-\mathrm{O}$ bonds and there are no $\mathrm{S}-\mathrm{S}$ bonds.

Therefore, there is not any $\mathrm{S}-\mathrm{S}$ bond in the Sulphur oxide trimer(${\mathrm{S}}_3{\mathrm{O}}_9$).