Question

SO2 is a reducing agent while TeO2is an oxidising agent ???

Answer 1

SO2 is reducing agent because sulphur has d orbital so it can easily expand its  +4 oxidation state to +6 oxidation state and can be behave as reducing agent but in TeO2 , Te is heaver  elements , - electrons are reluctant to take part in bond formation due to poor shielding of d- and f- orbital thus lower oxidation state (+2,-2) becomes more stable( inert pair effect) and hence TeO2 is oxidizing agent