Group-13 elements react with in amorphous form to form oxides of type . Which among the following is the most basic oxide?

JEE MainChemistry

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p-Block Elements: JEE Main Chemistry Question with Solution

Group-13 elements react with

\text{O}_2

in amorphous form to form oxides of type

\text{M}_2\text{O}_3\ (\text{M} = \text{element})

. Which among the following is the most basic oxide?

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A

\text{Al}_2\text{O}_3

B

\text{Ga}_2\text{O}_3

C

\text{Tl}_2\text{O}_3

D

\text{B}_2\text{O}_3

Step-by-step solutionView

Correct answer

Thallium(III) oxide ( $ext{Tl}_2 ext{O}_3$ ) is the most basic oxide among the Group-13 oxides because metallic character and basicity increase down the group.

Option analysis

Why each option works or fails

A ·

\text{Al}_2\text{O}_3

Believing that aluminium oxide is basic because aluminium is a common metal. Recognize that $\text{Al}_2\text{O}_3$ is amphoteric and reacts with both acids and strong bases.

B ·

\text{Ga}_2\text{O}_3

Assuming gallium oxide is more basic than thallium oxide due to incomplete group trends. Recall that $\text{Ga}_2\text{O}_3$ is still amphoteric, whereas oxides become distinctly basic only further down the group.

C ·

\text{Tl}_2\text{O}_3

None. This is the correct choice. Down Group 13 (B to Tl), electropositive and metallic character increase, shifting the nature of $\text{M}_2\text{O}_3$ from acidic ( $\text{B}_2\text{O}_3$ ) to amphoteric ( $\text{Al}_2\text{O}_3$ , $\text{Ga}_2\text{O}_3$ ) to predominantly basic ( $\text{In}_2\text{O}_3$ , $\text{Tl}_2\text{O}_3$ ).

D ·

\text{B}_2\text{O}_3

Confusing acidic and basic trends along a periodic table group. Recall that non-metallic oxides at the top of p-block groups, such as $\text{B}_2\text{O}_3$ , are acidic, not basic.

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Solution

StepWorking

✓quick_kill

Metallic character and electropositivity increase down Group 13, making basicity of $\text{M}_2\text{O}_3$ follow $\text{B}_2\text{O}_3\text{ (acidic)} < \text{Al}_2\text{O}_3,\,\text{Ga}_2\text{O}_3\text{ (amphoteric)} < \text{In}_2\text{O}_3\text{ (basic)} < \text{Tl}_2\text{O}_3\text{ (most basic)}$ ; hence, $\text{Tl}_2\text{O}_3$ is the most basic oxide.

Hints that build this answer step by step

How does the acid-base character of Group-13 oxides change descending from Boron to Thallium?
Basicity increases and acidity decreases down the group.
Which classification correctly describes the oxides of Group 13 in order from top to bottom?
$\text{B}_2\text{O}_3$ is acidic; $\text{Al}_2\text{O}_3$ and $\text{Ga}_2\text{O}_3$ are amphoteric; $\text{In}_2\text{O}_3$ and $\text{Tl}_2\text{O}_3$ are basic.

✓ Source and academic review

Question type: Single correct
Exam relevance: JEE Main · Chemistry
Concepts assessed: Chemistry
Academic status: Reviewed by official_key
Source: pyq
Editorial review: 8 September 2026

Answer

Thallium(III) oxide ( $ext{Tl}_2 ext{O}_3$ ) is the most basic oxide among the Group-13 oxides because metallic character and basicity increase down the group.

Why each option works or fails

A: $\text{Al}_2\text{O}_3$ - Believing that aluminium oxide is basic because aluminium is a common metal. Recognize that $\text{Al}_2\text{O}_3$ is amphoteric and reacts with both acids and strong bases.
B: $\text{Ga}_2\text{O}_3$ - Assuming gallium oxide is more basic than thallium oxide due to incomplete group trends. Recall that $\text{Ga}_2\text{O}_3$ is still amphoteric, whereas oxides become distinctly basic only further down the group.
C · correct: $\text{Tl}_2\text{O}_3$ - None. This is the correct choice. Down Group 13 (B to Tl), electropositive and metallic character increase, shifting the nature of $\text{M}_2\text{O}_3$ from acidic ( $\text{B}_2\text{O}_3$ ) to amphoteric ( $\text{Al}_2\text{O}_3$ , $\text{Ga}_2\text{O}_3$ ) to predominantly basic ( $\text{In}_2\text{O}_3$ , $\text{Tl}_2\text{O}_3$ ).
D: $\text{B}_2\text{O}_3$ - Confusing acidic and basic trends along a periodic table group. Recall that non-metallic oxides at the top of p-block groups, such as $\text{B}_2\text{O}_3$ , are acidic, not basic.

Step-by-step solution

quick_kill: Metallic character and electropositivity increase down Group 13, making basicity of $\text{M}_2\text{O}_3$ follow $\text{B}_2\text{O}_3\text{ (acidic)} < \text{Al}_2\text{O}_3,\,\text{Ga}_2\text{O}_3\text{ (amphoteric)} < \text{In}_2\text{O}_3\text{ (basic)} < \text{Tl}_2\text{O}_3\text{ (most basic)}$ ; hence, $\text{Tl}_2\text{O}_3$ is the most basic oxide.

p-Block Elements: JEE Main Chemistry Question with Solution

What feels right?

Thallium(III) oxide ( $ext{Tl}_2 ext{O}_3$ ) is the most basic oxide among the Group-13 oxides because metallic character and basicity increase down the group.

Why each option works or fails

Solution

✓quick_kill

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p-Block Elements: JEE Main Chemistry Question with Solution

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