Which of the following has S-S bonds?

H2S2O7H2S2O8H2S2O6H2S2O7 SO3)3 and why

A disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R–S–S–R.  H2S2O6 has S-S bond.

Let us first write the structures of all H2S2O7, H2S2O8, H2S2O6, H2S2O7. Then we can confirm the structure of H2S2O6 having S-S bond.

 H2S2O7 - Oleum – Pyrosulphuricacid (contains S-O-S bond)

  H2S2O8 – Peroxydisulphicacid (contains S-O-O-S bond)

H2S2O6 – Dithionicacid (contains S-S bond)

SO3 does not contain S-S bond.