Animated Solution for Chemistry - Periodicity in Properties: The option(s) with only amphoteric oxides is (are):

Welcome to a classic challenge from JEE Advanced! This question tests your mastery over the periodic table and the chemical nature of oxides.

We are asked to identify the options that contain only amphoteric oxides.

But what exactly does "amphoteric" mean? Imagine a chemical chameleon. An amphoteric oxide is a substance that can act as a base when it reacts with an acid, and it can act as an acid when it reacts with a base. It has a dual personality!

To conquer this problem, we need to systematically evaluate the chemical nature of every single oxide presented in the options.

Before we dive into the options, let's equip ourselves with a mental toolkit. How do we spot an amphoteric oxide in a crowd?

First, memorize the classic metals that form amphoteric oxides. A handy mnemonic is "Zanabe Ali Ne Bekar Gaya Punjabi Song", which gives us Zinc (Zn), Aluminum (Al), Beryllium (Be), Chromium (Cr), Gallium (Ga), Lead (Pb), and Tin (Sn).

Second, we must understand the behavior of transition metals like Chromium. Transition metals can exhibit multiple oxidation states, and their oxide nature changes accordingly.

The golden rule is: Lower oxidation states (like $+2$) are generally basic, because the metal can easily donate electrons. Higher oxidation states (like $+6$) are acidic. The intermediate oxidation states (like $+3$) hit the sweet spot and are amphoteric.

Options A and B

Let's put our toolkit to work, starting with Option A.

We see ${\text{Cr}}_2{\text{O}}_3$, $\text{SnO}$, and $\text{PbO}$. Based on our rules, Tin and Lead oxides are amphoteric. In ${\text{Cr}}_2{\text{O}}_3$, Chromium is in the $+3$ state, making it amphoteric too.

However, look closely at $\text{CrO}$. Here, Chromium is in a low $+2$ oxidation state. According to our golden rule, this makes $\text{CrO}$ a basic oxide. Because of this single basic intruder, Option A is incorrect.

Now, let's move to Option B.

The very first compound is $\text{NO}$ (Nitric oxide). You should instantly recognize this as a classic neutral oxide, along with ${\text{N}}_2\text{O}$ and $\text{CO}$.

Next is ${\text{B}}_2{\text{O}}_3$. Boron is a non-metal, and non-metal oxides are typically acidic. Even though the remaining oxides ($\text{PbO}$ and ${\text{SnO}}_2$) are amphoteric, the presence of neutral and acidic oxides completely disqualifies Option B.

Options C and D

Let's examine Option C.

We start with ${\text{Cr}}_2{\text{O}}_3$, which we already confirmed is amphoteric. Next is $\text{BeO}$. Beryllium is an exception in the alkaline earth metals; while others form basic oxides, $\text{BeO}$ is strictly amphoteric.

Then we have $\text{SnO}$ and ${\text{SnO}}_2$. Tin forms amphoteric oxides in both its common $+2$ and $+4$ oxidation states. Therefore, every single oxide in Option C is amphoteric!

Finally, let's verify Option D.

It starts with $\text{ZnO}$ and ${\text{Al}}_2{\text{O}}_3$. These are the absolute poster children for amphoteric oxides.

The last two are $\text{PbO}$ and ${\text{PbO}}_2$. Just like Tin, Lead belongs to Group 14 and forms amphoteric oxides in both its $+2$ and $+4$ states. Thus, all the oxides in Option D are also amphoteric!

By systematically applying our rules, we successfully filtered out the incorrect options. Option A failed due to basic $\text{CrO}$, and Option B failed due to neutral $\text{NO}$ and acidic ${\text{B}}_2{\text{O}}_3$.

Options C and D passed with flying colors, containing exclusively amphoteric oxides. Since this is a multiple-correct question, our final answer is (C) and (D).