The most basic oxide among the following is: Na2​O,Al2​O3​,SiO2​,P2​O5​?

1. The most basic oxide among the following is: Na₂O, Al₂O₃, SiO₂, P₂O₅ +

Answer

Na₂O — Sodium oxide

Detailed Explanation

Across Period 3, the nature of oxides changes from basic → amphoteric → acidic.

Na₂O → Al₂O₃ → SiO₂ → P₂O₅

Na₂O is a strongly basic oxide. It reacts with water to form sodium hydroxide:

Na₂O + H₂O → 2NaOH

NaOH is a strong base, so Na₂O shows strongly basic character.

Al₂O₃ is amphoteric, meaning it reacts with both acids and bases.

SiO₂ and P₂O₅ are acidic oxides.

Basic character decreases from left → right across Period 3.

Practical Trend

Na₂O Strongly Basic
Highest basic character

Al₂O₃ Amphoteric
Acid + Base

SiO₂ Acidic
Weakly acidic

P₂O₅ Acidic
More acidic

Why Does Basic Character Decrease?

From Na to P across Period 3:

• Nuclear charge increases.
• Atomic size decreases.
• Electronegativity generally increases.
• Metallic character decreases.
• Covalent character of oxides increases.
• Therefore, basic character decreases and acidic character increases.

Metallic character ↓   ⇒   Basic character of oxide ↓

Hence, among the given oxides, Na₂O is the most basic.

30 Related MCQs with Solutions

1. The most basic oxide among Na₂O, Al₂O₃, SiO₂ and P₂O₅ is:

A. Na₂O

B. Al₂O₃

C. SiO₂

D. P₂O₅

Answer: A. Na₂O
It is a strongly basic oxide.

2. Which oxide is amphoteric?

A. Na₂O

B. Al₂O₃

C. SiO₂

D. P₂O₅

Answer: B. Al₂O₃

3. Which oxide is acidic?

A. Na₂O

B. MgO

C. SiO₂

D. NaOH

Answer: C. SiO₂

4. The nature of Period 3 oxides generally changes from:

A. Acidic → basic

B. Basic → amphoteric → acidic

C. Neutral → basic

D. Acidic → amphoteric → basic

Answer: B

5. Na₂O reacts with water to form:

A. NaCl

B. NaOH

C. HCl

D. Na₂CO₃

Answer: B. NaOH

6. The reaction Na₂O + H₂O gives:

A. NaOH

B. H₂O₂

C. NaH

D. O₂

Answer: A. NaOH

7. Basic character of oxides across Period 3:

A. Increases

B. Decreases

C. Remains constant

D. First decreases then increases

Answer: B. Decreases

8. Acidic character of oxides across Period 3 generally:

A. Increases

B. Decreases

C. Remains unchanged

D. Becomes zero

Answer: A. Increases

9. Which element forms the strongly basic oxide Na₂O?

A. Na

B. Al

C. Si

D. P

Answer: A. Sodium

10. Al₂O₃ can react with both:

A. Only acids

B. Only bases

C. Acids and bases

D. Neither

Answer: C. Acids and bases

11. SiO₂ is generally classified as:

A. Basic oxide

B. Amphoteric oxide

C. Acidic oxide

D. Neutral oxide

Answer: C. Acidic oxide

12. P₂O₅ is:

A. Basic

B. Acidic

C. Neutral

D. Metallic

Answer: B. Acidic

13. Which oxide has the greatest basic character?

A. Na₂O

B. Al₂O₃

C. SiO₂

D. P₂O₅

Answer: A. Na₂O

14. Which property decreases from Na to P?

A. Non-metallic character

B. Electronegativity

C. Metallic character

D. Nuclear charge

Answer: C. Metallic character

15. Which property increases from Na to P across Period 3?

A. Atomic size

B. Metallic character

C. Electronegativity

D. Basic character of oxides

Answer: C. Electronegativity

16. A basic oxide generally reacts with an acid to form:

A. Salt and water

B. Only oxygen

C. Only hydrogen

D. Metal only

Answer: A. Salt and water

17. Which oxide shows both acidic and basic behaviour?

A. Na₂O

B. Al₂O₃

C. P₂O₅

D. SO₃

Answer: B. Al₂O₃

18. The oxide of a highly electropositive metal is generally:

A. Basic

B. Acidic

C. Neutral

D. Always amphoteric

Answer: A. Basic

19. Which one is the most acidic among the given Period 3 oxides?

A. Na₂O

B. Al₂O₃

C. SiO₂

D. P₂O₅

Answer: D. P₂O₅

20. The decrease in basicity across a period is mainly related to:

A. Increase in metallic character

B. Decrease in metallic character

C. Decrease in nuclear charge

D. Increase in atomic size

Answer: B

21. Which oxide is formed by a Group 1 element?

A. Na₂O

B. SiO₂

C. P₂O₅

D. Al₂O₃

Answer: A. Na₂O

22. Which oxide is predominantly covalent?

A. Na₂O

B. SiO₂

C. NaOH

D. NaCl

Answer: B. SiO₂

23. Which oxide is associated with the highest metallic character among the given elements?

A. Na₂O

B. Al₂O₃

C. SiO₂

D. P₂O₅

Answer: A. Na₂O

24. Which statement is correct?

A. Basicity increases from Na to P

B. Basicity decreases from Na to P

C. All oxides are equally basic

D. All oxides are neutral

Answer: B

25. Which oxide reacts with both HCl and NaOH?

A. Na₂O

B. Al₂O₃

C. SiO₂ only

D. P₂O₅

Answer: B. Al₂O₃

26. Which oxide gives an alkaline solution with water?

A. Na₂O

B. SiO₂

C. P₂O₅

D. CO₂

Answer: A. Na₂O
Na₂O + H₂O → 2NaOH.

27. Which trend is observed in the oxides of Period 3?

A. Basic → amphoteric → acidic

B. Acidic → basic → amphoteric

C. Neutral → basic

D. Basic → neutral only

Answer: A

28. The most electropositive element among Na, Al, Si and P is:

A. Na

B. Al

C. Si

D. P

Answer: A. Na

29. Which oxide represents the most basic character among the following?

A. CO₂

B. SO₂

C. Na₂O

D. P₂O₅

Answer: C. Na₂O

30. The correct order of basic character of the given oxides is:

A. Na₂O > Al₂O₃ > SiO₂ > P₂O₅

B. P₂O₅ > SiO₂ > Al₂O₃ > Na₂O

C. SiO₂ > Na₂O > P₂O₅ > Al₂O₃

D. Al₂O₃ > Na₂O > P₂O₅ > SiO₂

Answer: A
Across Period 3, metallic character decreases, so the basic character of the oxides decreases.

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