The incorrect statement among the following is options .

Let us analyze each statement:

Option 1: $$PH_3$$ shows lower proton affinity than $$NH_3$$. This is correct because N is more electronegative and smaller, making the lone pair on $$NH_3$$ more available for proton bonding.

Option 2: $$SO_2$$ can act as an oxidizing agent, but not as a reducing agent. This is incorrect. $$SO_2$$ can act as both an oxidizing agent and a reducing agent. As a reducing agent, S in $$SO_2$$ (+4 oxidation state) can be oxidized to +6 (e.g., $$SO_3$$ or $$H_2SO_4$$). As an oxidizing agent, it can be reduced to S or $$H_2S$$.

Option 3: $$PF_3$$ exists but $$NF_5$$ does not. This is correct. Nitrogen cannot form $$NF_5$$ because it lacks d-orbitals and cannot expand its octet beyond 4 bonds.

Option 4: $$NO_2$$ can dimerise easily. This is correct. $$NO_2$$ has an unpaired electron and readily dimerises to form $$N_2O_4$$.

The incorrect statement is Option 2.

The correct answer is Option 2.