Among the following oxides of p-block elements: $$Cl_2O_7$$, $$CO$$, $$PbO_2$$, $$N_2O$$, $$NO$$, $$Al_2O_3$$, $$SiO_2$$, $$N_2O_5$$, $$SnO_2$$, the number of amphoteric oxides is:

We need to identify the amphoteric oxides among: $$Cl_2O_7$$, $$CO$$, $$PbO_2$$, $$N_2O$$, $$NO$$, $$Al_2O_3$$, $$SiO_2$$, $$N_2O_5$$, $$SnO_2$$.

An amphoteric oxide reacts with both acids and bases.

$$Cl_2O_7$$: Acidic oxide (anhydride of $$HClO_4$$). Not amphoteric.

$$CO$$: Neutral oxide. Not amphoteric.

$$PbO_2$$: Amphoteric oxide. Lead(IV) oxide reacts with acids (e.g., $$PbO_2 + 4HCl \rightarrow PbCl_4 + 2H_2O$$) and with bases (e.g., forming plumbates). Yes, amphoteric.

$$N_2O$$: Neutral oxide. Not amphoteric.

$$NO$$: Neutral oxide. Not amphoteric.

$$Al_2O_3$$: Amphoteric oxide. Reacts with acids to form aluminum salts and with bases to form aluminates. Yes, amphoteric.

$$SiO_2$$: Acidic oxide. Not amphoteric.

$$N_2O_5$$: Acidic oxide (anhydride of $$HNO_3$$). Not amphoteric.

$$SnO_2$$: Amphoteric oxide. Tin(IV) oxide reacts with acids and bases. Yes, amphoteric.

The amphoteric oxides are: $$PbO_2$$, $$Al_2O_3$$, and $$SnO_2$$. That gives us 3.

The answer is 3.