The correct statements among I to III regarding group 13 element oxides are:
I. Boron trioxide is ac

Q: Why exactly is Boron oxide considered acidic?

Boron is a non-metal with a relatively high electronegativity. When it forms bonds with oxygen, the resulting $B_2O_3$ is covalent. When dissolved in water, it forms boric acid ($H_3BO_3$), which acts as a Lewis acid by accepting a hydroxide ion from water, thereby releasing $H^+$ ions into the solution.

Q: What does it mean for an oxide to be 'amphoteric'?

An amphoteric oxide is one that can behave as both an acid and a base depending on what it is reacting with. For example, $Al_2O_3$ will react with a strong acid like $HCl$ to form a salt and water, but it will also react with a strong base like $NaOH$ to form sodium aluminate.

Q: Why does the metallic character increase down the group?

As you move down a group, new electron shells are added, making the atom larger. The outermost electrons are further from the nucleus and experience more shielding from inner electrons. This makes it easier for the atom to lose its outer electrons (lower ionization energy), which is the defining characteristic of a metal.

Q: Does the oxidation state change down Group 13?

Yes, while the group oxidation state is $+3$, the $+1$ oxidation state becomes increasingly stable as you move down the group, especially for Thallium. This is due to the 'inert pair effect', where the $ns^2$ electrons become reluctant to participate in bonding.

Q: Are there any exceptions to these oxide trends?

While the general trend holds true, the oxidation state of the metal also plays a crucial role. For transition metals, higher oxidation states (like $+7$ in $Mn_2O_7$) are highly covalent and acidic, while lower oxidation states (like $+2$ in $MnO$) are ionic and basic. However, for Group 13, the trend described in the question is standard.

Question

The correct statements among I to III regarding group 13 element oxides are:
I. Boron trioxide is acidic.
II. Oxides of aluminium and gallium are amphoteric.
III. Oxides of indium and thallium are basic.

Options:

(A) I, II and III

(B) I and III only

(C) I and II only

(D) II and III only

Sigma Percentile · Accepted Answer

### Analyzing the Setup

When we look at the Group 13 elements of the periodic table, we are observing a fascinating transition. At the very top, we have Boron ($B$), followed by Aluminium ($Al$), Gallium ($Ga$), Indium ($In$), and finally Thallium ($Tl$) at the bottom.

To understand the chemical behavior of their oxides, we must first visualize what happens to the atoms themselves as we move down this vertical column. With each step down, a new principal electron shell is added. This causes the atomic radius to increase significantly. Because the outermost valence electrons are now further away from the positive pull of the nucleus, the ionization energy—the energy required to strip an electron away—steadily decreases.

### The Master Rule of Oxides

What does this mean for the element's character? An element that easily loses electrons is, by definition, more metallic. Therefore, as we descend Group 13, the **metallic character increases**.

This brings us to a fundamental rule in inorganic chemistry regarding the nature of oxides:
*   **Non-metal oxides** tend to be acidic.
*   **True metal oxides** tend to be basic.
*   Oxides of elements with **intermediate character** (metalloids or weak metals) are usually amphoteric, meaning they can react with both acids and bases.

### Classifying the Group 13 Oxides

Let's apply this master rule to our specific elements.

Boron, sitting at the top of the group, is a distinct non-metal. Consequently, its oxide, Boron trioxide ($B_2O_3$), is **acidic**. It will readily react with basic oxides to form metal borates.

As we move down to Aluminium and Gallium, the metallic character is intermediate. They are metals, but their relatively high charge density makes their bonds with oxygen somewhat covalent. As a result, Aluminium oxide ($Al_2O_3$) and Gallium oxide ($Ga_2O_3$) are **amphoteric**.

Finally, reaching the bottom of the group, Indium and Thallium are distinct, heavy metals with low ionization energies. Their oxides, such as Indium(III) oxide ($In_2O_3$) and Thallium(I) oxide ($Tl_2O$), are distinctly **basic** in nature.

### Final Conclusion

Evaluating the given statements against our chemical logic:
*   **Statement I:** Boron trioxide is acidic. (True)
*   **Statement II:** Oxides of aluminium and gallium are amphoteric. (True)
*   **Statement III:** Oxides of indium and thallium are basic. (True)

Since all the statements perfectly align with the periodic trends, the correct option is the one that includes all three.

Animated Solution for Chemistry - s and p-Block Elements: The correct statements among I to III regarding group 13 element oxides are: I. Boron trioxide is acidic. II. Oxides of aluminium and gallium are amphoteric. III. Oxides of indium and thallium are basic.

Select Answer:

Visualized Solution

$Group 13 Elements$

$Periodic Trends Down the Group$

$Nature of Oxides$

$Classifying Group 13 Oxides$

$Evaluating the Statements$

$The Inert Pair Effect$

The Sigma Insight: Group 13 Elements

Analyzing the Setup

The Master Rule of Oxides

Classifying the Group 13 Oxides

Final Conclusion

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