SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs (2026–27) – Assam Eduverse
The SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs (2026–27) are designed as per the latest ASSEB syllabus and updated board exam pattern. These SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs include important objective questions, numerical-based MCQs, and concept-focused practice sets to help students prepare effectively for exams.
Prepared by subject experts of Assam Eduverse, these SEBA Class 9 Science Chapter 3 MCQs cover key topics such as laws of chemical combination, Dalton’s atomic theory, atomic and molecular mass, mole concept, valency, and chemical formulae. Practicing these Atoms and Molecules MCQs Class 9 SEBA and Assam Board Class 9 Science objective questions improves conceptual clarity and problem-solving accuracy. For more practice, explore Class 9 Science chapterwise MCQs and SEBA Class 9 MCQs.
Regular revision of these ASSEB Class 9 Science Important MCQs ensures strong preparation and better performance in exams. You can also check the detailed solutions here: SEBA Class 9 Science Chapter 3 Atoms and Molecules Solutions, or explore complete resources from SEBA Class 9 & 10 study materials and SEBA Class 9 syllabus.
SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs – ASSEB 2026–27 Board Exam Practice
Table of Contents
Q1. Who proposed that matter is made up of indivisible particles called atoms?
a) Lavoisier
b) John Dalton
c) Proust
d) Berzilius
Answer: b) John Dalton
Q2. The law which states that mass can neither be created nor destroyed in a chemical reaction is called:
a) Law of definite proportions
b) Law of multiple proportions
c) Law of conservation of mass
d) Atomic theory
Answer: c) Law of conservation of mass
Q3. The law of constant proportions was stated by:
a) Dalton
b) Lavoisier
c) Proust
d) Democritus
Answer: c) Proust
Q4. In water, the ratio of mass of hydrogen to oxygen is:
a) 1 : 2
b) 2 : 1
c) 1 : 8
d) 8 : 1
Answer: c) 1 : 8
Q5. Atoms of different elements differ in:
a) Colour only
b) Mass and chemical properties
c) Size only
d) Shape only
Answer: b) Mass and chemical properties
Q6. Atomic radius is measured in:
a) metre
b) centimetre
c) nanometre
d) millimetre
Answer: c) nanometre
Q7. 1 nanometre is equal to:
a) 10⁻⁶ m
b) 10⁻⁹ m
c) 10⁻³ m
d) 10⁻¹² m
Answer: b) 10⁻⁹ m
Q8. Which of the following is a monoatomic molecule?
a) Oxygen
b) Nitrogen
c) Argon
d) Chlorine
Answer: c) Argon
Q9. The number of atoms present in one molecule of oxygen (O₂) is:
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Q10. The atomicity of phosphorus is:
a) 1
b) 2
c) 4
d) 8
Answer: c) 4
Q11. Which of the following is a polyatomic ion?
a) Na⁺
b) Cl⁻
c) OH⁻
d) H⁺
Answer: c) OH⁻
Q12. The valency of oxygen is:
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Q13. The chemical formula of calcium oxide is:
a) Ca₂O
b) CaO₂
c) CaO
d) Ca₂O₂
Answer: c) CaO
Q14. The chemical formula of aluminium oxide is:
a) AlO
b) Al₂O₃
c) Al₃O₂
d) AlO₃
Answer: b) Al₂O₃
Q15. The molecular mass of water (H₂O) is:
a) 16 u
b) 17 u
c) 18 u
d) 20 u
Answer: c) 18 u
Q16. The formula unit mass of NaCl is:
a) 23 u
b) 35.5 u
c) 58.5 u
d) 46 u
Answer: c) 58.5 u
Q17. One mole of any substance contains:
a) 6.022 × 10²³ particles
b) 6.022 × 10²² particles
c) 6.022 × 10²⁴ particles
d) 3.011 × 10²³ particles
Answer: a) 6.022 × 10²³ particles
Q18. The SI unit of amount of substance is:
a) gram
b) kilogram
c) mole
d) atomic mass unit
Answer: c) mole
Q19. The molar mass of hydrogen atom is:
a) 1 g
b) 2 g
c) 1 u
d) 2 u
Answer: a) 1 g
Q20. The formula of ammonium sulphate is:
a) NH₄SO₄
b) (NH₄)₂SO₄
c) NH₄₂SO₄
d) NH₄(SO₄)₂
Answer: b) (NH₄)₂SO₄
Q21. Assertion: Mass remains constant during a chemical reaction.
Reason: Atoms are neither created nor destroyed in a chemical reaction.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q22. Assertion: Water always contains hydrogen and oxygen in the ratio 1:8 by mass.
Reason: Elements in a compound are present in definite proportions by mass.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q23. Assertion: Atoms of the same element have identical chemical properties.
Reason: Atoms of the same element have identical mass.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: b) Both A and R are true but R is not the correct explanation of A
Q24. Assertion: Argon is monoatomic.
Reason: Argon molecule contains only one atom.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q25. Assertion: One mole of oxygen molecules contains 6.022 × 10²³ molecules.
Reason: Mole is the SI unit of mass.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: c) A is true but R is false
Q26. Assertion: Atomic mass unit is defined using carbon-12 isotope.
Reason: One atomic mass unit is equal to one-twelfth the mass of one carbon-12 atom.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q27. Assertion: Metals and some elements like carbon do not have simple molecular structures.
Reason: They consist of a very large and indefinite number of atoms bonded together.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q28. Assertion: The formula of calcium hydroxide is Ca(OH)₂.
Reason: Brackets are used when more than one polyatomic ion is present.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q29. Assertion: Molecular mass is the sum of atomic masses of all atoms in a molecule.
Reason: Molecular mass is expressed in atomic mass unit (u).
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: b) Both A and R are true but R is not the correct explanation of A
Q30. Assertion: In ionic compounds, charges on ions must balance.
Reason: Overall structure of an ionic compound must be neutral.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: a) Both A and R are true and R is the correct explanation of A
Q31. Which of the following statements are correct about Dalton’s atomic theory?
i) Atoms are indivisible.
ii) Atoms can be created in a chemical reaction.
iii) Atoms combine in simple whole number ratios.
a) i and iii only
b) i and ii only
c) ii and iii only
d) i, ii and iii
Answer: a) i and iii only
Q32. Which of the following are diatomic molecules?
i) O₂
ii) N₂
iii) Ar
a) i and ii only
b) ii and iii only
c) i and iii only
d) i, ii and iii
Answer: a) i and ii only
Q33. Which of the following are polyatomic ions?
i) SO₄²⁻
ii) NH₄⁺
iii) Cl⁻
a) i and ii only
b) ii and iii only
c) i and iii only
d) i, ii and iii
Answer: a) i and ii only
Q34. Which of the following follow the law of definite proportions?
i) Mixture
ii) Compound
iii) Solution
iv) Alloy
a) ii only
b) i and ii
c) ii and iii
d) i, ii, iii and iv
Answer: a) ii only
Q35. Which of the following represents Avogadro number?
i) 6.022 × 10²³
ii) 6.022 × 10²²
iii) 3.011 × 10²³
iv) 1 × 10²³
a) i only
b) i and ii
c) ii and iii
d) i, ii, iii and iv
Answer: a) i only
Q36. Which of the following is a binary compound?
i) NaCl
ii) NH₄Cl
iii) Na₂SO₄
iv) Ca(OH)₂
a) i only
b) i and ii
c) ii and iii
d) i, ii, iii and iv
Answer: a) i only
Q37. Which of the following formulae are correct?
i) MgCl₂
ii) Na₂CO₃
iii) CaCl
a) i and ii only
b) ii and iii only
c) i and iii only
d) i, ii and iii
Answer: a) i and ii only
Q38. Molar mass of oxygen molecule (O₂) is:
a) 16 g
b) 32 g
c) 8 g
d) 2 g
Answer: b) 32 g
Q39. One mole of carbon atoms weighs:
a) 6 g
b) 12 g
c) 18 g
d) 24 g
Answer: b) 12 g
Q40. Which of the following is tetra-atomic?
a) Nitrogen
b) Oxygen
c) Phosphorus
d) Chlorine
Answer: c) Phosphorus
Q41. Match the following:
| Column A | Column B |
|---|---|
| 1) Law of conservation of mass | a) 6.022 × 10²³ particles |
| 2) Law of definite proportions | b) 1/12th mass of carbon-12 |
| 3) Atomic mass unit | c) Mass remains constant |
| 4) Mole | d) Fixed proportion by mass |
a) 1-c, 2-d, 3-b, 4-a
b) 1-d, 2-c, 3-a, 4-b
c) 1-c, 2-b, 3-d, 4-a
d) 1-a, 2-d, 3-b, 4-c
Answer: a) 1-c, 2-d, 3-b, 4-a
Q42. Match the following:
| Column A | Column B |
|---|---|
| 1) H₂O | a) Ozone |
| 2) NH₃ | b) Ammonia |
| 3) CO₂ | c) Water |
| 4) O₃ | d) Carbon dioxide |
a) 1-c, 2-b, 3-d, 4-a
b) 1-b, 2-c, 3-a, 4-d
c) 1-c, 2-d, 3-b, 4-a
d) 1-a, 2-b, 3-c, 4-d
Answer: a) 1-c, 2-b, 3-d, 4-a
Q43. Match the following:
| Column A | Column B |
|---|---|
| 1) Na⁺ | a) Cation |
| 2) Cl⁻ | b) Anion |
| 3) SO₄²⁻ | c) Polyatomic ion |
| 4) NH₄⁺ | d) Positively charged ion |
a) 1-a, 2-b, 3-c, 4-d
b) 1-d, 2-b, 3-c, 4-a
c) 1-a, 2-c, 3-b, 4-d
d) 1-d, 2-a, 3-c, 4-b
Answer: b) 1-d, 2-b, 3-c, 4-a
Q44. Match the following atomic masses:
| Column A | Column B |
|---|---|
| 1) Hydrogen | a) 12 u |
| 2) Oxygen | b) 1 u |
| 3) Nitrogen | c) 16 u |
| 4) Carbon | d) 14 u |
a) 1-b, 2-c, 3-d, 4-a
b) 1-a, 2-b, 3-c, 4-d
c) 1-b, 2-d, 3-c, 4-a
d) 1-c, 2-b, 3-a, 4-d
Answer: a) 1-b, 2-c, 3-d, 4-a
SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs – Important Objective Questions
Building a strong foundation in Atoms and Molecules is crucial for understanding advanced concepts in Chemistry. Practicing well-structured MCQs based on the latest SEBA (ASSEB) syllabus helps students strengthen their basics and become familiar with the types of objective questions asked in examinations.
These SEBA Class 9 Science Chapter 3 MCQs are designed to cover important topics such as the laws of chemical combination, Dalton’s atomic theory, atomic and molecular masses, valency, chemical formula writing, and the mole concept. Since this chapter includes both theory and numerical-based questions, regular practice is essential for developing accuracy and confidence.
Solving these important MCQs for Class 9 Science allows students to improve their problem-solving skills, especially in numerical calculations related to moles and mass relationships. It also helps in avoiding common errors while balancing equations, writing correct chemical formulae, and understanding fundamental principles.
Consistent revision through objective questions enhances speed, precision, and conceptual clarity. Students become more comfortable with exam patterns, manage time effectively, and can quickly revise key concepts before tests or final exams.
For better performance in school assessments and board-level examinations, students should make these MCQs a regular part of their study routine. With clear concepts and continuous practice, scoring well in this chapter becomes much more achievable and less stressful.
FAQs – SEBA Class 9 Science Chapter 3 Atoms and Molecules MCQs
1. How many MCQs come from Atoms and Molecules in SEBA Class 9 exam?
Around 45 MCQs come from the Science paper overall. Expect 3–5 questions from this chapter, so practice basics like mole concept carefully.
2. Which are the most important MCQs from Class 9 Science Chapter 3 SEBA?
Focus on laws of chemical combination, mole calculations, and atomic mass. These are repeated topics, so revise formulas and definitions properly.
3. Are numericals asked in Atoms and Molecules MCQs SEBA Class 9?
Yes, simple numericals based on mole and mass are common. Practice conversions like grams to moles to avoid confusion in MCQ options.
4. Where can I download SEBA Class 9 Science Chapter 3 MCQs with answers?
You can find chapter-wise MCQs with solutions on Assam Eduverse. Always choose updated PDFs based on latest ASSEB exam pattern.
5. Is Atoms and Molecules a difficult chapter for SEBA students?
It feels tough initially, but becomes easy with formula practice. Focus on concepts like Avogadro number and mole to build confidence.
6. How to score full marks in Atoms and Molecules MCQs SEBA Class 9?
Practice daily MCQs and revise formulas regularly. Assam Eduverse mock tests can help improve speed and accuracy before exams.
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