Class 9 Science Chapter 9 Atomic Foundations of Matter MCQ questions from the NCERT book. In addition to the MCQs, we also have 10 fill in the blanks, 10 true and false questions and 1 match the following question. Below we have some important points from the chapter –
- Mass remains unchanged during physical changes.
- Mass remains conserved in chemical reactions.
- Law of Conservation of Mass by Lavoisier.
- Matter cannot be created or destroyed.
- Compounds contain elements in fixed mass ratios.
- Law of Constant Proportions by Proust.
- Water contains hydrogen and oxygen in 1:8.
- Dalton’s Atomic Theory explains matter composition.
- Atoms combine in simple whole-number ratios.
- Molecules consist of two or more atoms.
- Chemical bonds hold atoms together.
- Covalent bonds form by electron sharing.
- Ionic bonds form by electron transfer.
- Ions include positively and negatively charged particles.
- Chemical formulae represent compound composition.
35 MCQ Questions for Class 9 Science: Chapter 9 Atomic Foundations of Matter
Question 1. Who proposed the Law of Conservation of Mass?
a) Dalton
b) Rutherford
c) Lavoisier
d) Proust
Answer:
c) Lavoisier — Father of Modern Chemistry.
Question 2. Mass remains unchanged during a ________ change.
a) Physical
b) Nuclear
c) Radioactive
d) Biological
Answer:
a) Physical — Salt solution activity.
Question 3. Matter can neither be created nor destroyed.
a) Proust’s Law
b) Conservation of Mass
c) Octet Rule
d) Atomic Number
Answer:
b) Conservation of Mass — Total mass remains constant.
Question 4. Vinegar reacts with baking soda to produce:
a) Oxygen
b) Nitrogen
c) Carbon dioxide
d) Hydrogen
Answer:
c) Carbon dioxide — Effervescence indicates gas formation.
Question 5. Who proposed the Law of Constant Proportions?
a) Dalton
b) Thomson
c) Lavoisier
d) Proust
Answer:
d) Proust — Fixed mass ratio concept.
Question 6. Water contains hydrogen and oxygen in ratio:
a) 1:2
b) 2:1
c) 1:8
d) 8:1
Answer:
c) 1:8 — By mass, not atoms.
Question 7. Law of Constant Proportions is also called:
a) Proust’s Law
b) Boyle’s Law
c) Ohm’s Law
d) Avogadro’s Law
Answer:
a) Proust’s Law — Same composition always.
Question 8. Dalton’s theory states matter is made of:
a) Molecules
b) Ions
c) Atoms
d) Electrons
Answer:
c) Atoms — Fundamental particles.
Question 9. Dalton considered atoms to be:
a) Divisible
b) Indivisible
c) Charged
d) Radioactive
Answer:
b) Indivisible — Original atomic theory.
Question 10. Atoms combine in ______ ratios.
a) Random
b) Decimal
c) Whole-number
d) Fractional
Answer:
c) Whole-number — Dalton’s postulate.
Question 11. A molecule is electrically:
a) Positive
b) Negative
c) Neutral
d) Variable
Answer:
c) Neutral — Net charge zero.
Question 12. Helium generally exists as:
a) Molecules
b) Atoms
c) Ions
d) Compounds
Answer:
b) Atoms — Already stable.
Question 13. The force holding atoms together is:
a) Gravity
b) Magnetism
c) Chemical bond
d) Friction
Answer:
c) Chemical bond — Stabilizes atoms.
Question 14. Covalent bonds form by:
a) Electron transfer
b) Proton transfer
c) Electron sharing
d) Neutron transfer
Answer:
c) Electron sharing — Shared electron pairs.
Question 15. Hydrogen molecule formula is:
a) H
b) H₂
c) H₃
d) He
Answer:
b) H₂ — Two hydrogen atoms.
Question 16. H—H represents a:
a) Double bond
b) Triple bond
c) Single bond
d) Ionic bond
Answer:
c) Single bond — One shared pair.
Question 17. Chlorine molecule is represented as:
a) Cl
b) Cl₂
c) Cl₃
d) Cl⁻
Answer:
b) Cl₂ — Two chlorine atoms.
Question 18. Oxygen atoms share _____ electrons each.
a) One
b) Two
c) Three
d) Four
Answer:
b) Two — Forms double bond.
Question 19. Oxygen molecule contains a:
a) Single bond
b) Double bond
c) Triple bond
d) Ionic bond
Answer:
b) Double bond — O=O representation.
Question 20. Hydrogen chloride formula is:
a) HCl
b) H₂Cl
c) HCl₂
d) H₂Cl₂
Answer:
a) HCl — One hydrogen, one chlorine.
Question 21. Water molecule formula is:
a) HO
b) H₂O
c) H₂O₂
d) OH
Answer:
b) H₂O — Two hydrogens, one oxygen.
Question 22. Carbon monoxide is written as:
a) CO
b) CO₂
c) C₂O
d) C₂O₂
Answer:
a) CO — One oxygen atom.
Question 23. CO₂ is named:
a) Carbon oxide
b) Carbon monoxide
c) Carbon dioxide
d) Dicarbon oxide
Answer:
c) Carbon dioxide — Prefix di means two.
Question 24. NH₃ is commonly called:
a) Methane
b) Water
c) Ammonia
d) Nitrogen oxide
Answer:
c) Ammonia — Common name used.
Question 25. H₂S is named:
a) Dihydrogen sulfide
b) Hydrogen sulfide
c) Sulfur hydride
d) Hydrogen disulfide
Answer:
b) Hydrogen sulfide — Special naming rule.
Question 26. Ionic bonds form by:
a) Sharing electrons
b) Electron transfer
c) Neutron transfer
d) Proton sharing
Answer:
b) Electron transfer — Produces ions.
Question 27. Sodium loses one electron to form:
a) Na⁻
b) Na²⁺
c) Na⁺
d) Na
Answer:
c) Na⁺ — Positive ion formed.
Question 28. Chlorine gains one electron to form:
a) Cl⁺
b) Cl²⁺
c) Cl⁻
d) Cl
Answer:
c) Cl⁻ — Negative ion formed.
Question 29. Positively charged ions are called:
a) Anions
b) Cations
c) Molecules
d) Atoms
Answer:
b) Cations — Electron loss.
Question 30. Negatively charged ions are called:
a) Cations
b) Atoms
c) Anions
d) Molecules
Answer:
c) Anions — Electron gain.
Question 31. NaCl is an example of:
a) Covalent compound
b) Ionic compound
c) Element
d) Mixture
Answer:
b) Ionic compound — Electron transfer involved.
Question 32. Oppositely charged ions attract due to:
a) Friction
b) Gravity
c) Electrostatic force
d) Magnetism
Answer:
c) Electrostatic force — Creates ionic bond.
Question 33. Sodium chloride forms:
a) Single molecules
b) 3-D crystals
c) Gas particles
d) Liquid clusters
Answer:
b) 3-D crystals — Repeating ionic arrangement.
Question 34. Sulfide ion is represented as:
a) S⁺
b) S⁻
c) S²⁻
d) S²⁺
Answer:
c) S²⁻ — Gains two electrons.
Question 35. Which compound follows fixed composition?
a) Air
b) Salt solution
c) Water
d) Soil
Answer:
c) Water — Definite mass ratio.
10 True and False Questions for Chapter 9 Atomic Foundations of Matter
Question 1. Mass is conserved during chemical reactions. (True/False)
Answer:
True
Question 2. Matter can be created during a reaction. (True/False)
Answer:
False
Question 3. Water always contains hydrogen and oxygen in a fixed ratio. (True/False)
Answer:
True
Question 4. Dalton proposed that atoms are divisible particles. (True/False)
Answer:
False
Question 5. Molecules are formed by chemically bonded atoms. (True/False)
Answer:
True
Question 6. Covalent bonds are formed by electron transfer. (True/False)
Answer:
False
Question 7. Oxygen molecule contains a double covalent bond. (True/False)
Answer:
True
Question 8. Sodium chloride is an ionic compound. (True/False)
Answer:
True
Question 9. Anions are positively charged ions. (True/False)
Answer:
False
Question 10. Ionic compounds form crystal lattices. (True/False)
Answer:
True
10 Fill in the Blanks Questions for Chapter 9 Atomic Foundations of Matter
Question 1. The Law of Conservation of Mass was proposed by __________.
Answer:
Lavoisier
Question 2. According to the Law of Constant Proportions, compounds contain elements in a fixed __________ ratio.
Answer:
Mass
Question 3. Dalton proposed that all matter is made of tiny particles called __________.
Answer:
Atoms
Question 4. A group of chemically bonded atoms forms a __________.
Answer:
Molecule
Question 5. The force that holds atoms together is called a chemical __________.
Answer:
Bond
Question 6. In a covalent bond, atoms __________ electrons.
Answer:
Share
Question 7. The chemical formula of water is __________.
Answer:
H₂O
Question 8. Ionic bonds are formed by the __________ of electrons.
Answer:
Transfer
Question 9. Positively charged ions are called __________.
Answer:
Cations
Question 10. Sodium chloride forms a three-dimensional __________ lattice.
Answer:
Crystal
Question on Match the Columns
Unmatched Columns – Questions
| Column A | Column B |
|---|---|
| (i) Law of Conservation of Mass | (a) Fixed mass ratio in compounds |
| (ii) Law of Constant Proportions | (b) Positively charged ion |
| (iii) Covalent Bond | (c) Electron sharing between atoms |
| (iv) Ionic Bond | (d) Matter cannot be created or destroyed |
| (v) Cation | (e) Formed by electron transfer |
| (vi) Anion | (f) Negatively charged ion |
Matched Columns – Answer
| Column A | Column B |
|---|---|
| (i) Law of Conservation of Mass | (d) Matter cannot be created or destroyed |
| (ii) Law of Constant Proportions | (a) Fixed mass ratio in compounds |
| (iii) Covalent Bond | (c) Electron sharing between atoms |
| (iv) Ionic Bond | (e) Formed by electron transfer |
| (v) Cation | (b) Positively charged ion |
| (vi) Anion | (f) Negatively charged ion |
Related Class 9 Chemistry Chapters
Study these together for full marks in the chemistry section:
- Journey Inside the Atom MCQs – protons, neutrons and electrons.
- Exploring Mixtures and their Separation MCQs – elements, compounds, mixtures.
- Earth as a System MCQs – how matter cycles through nature.
Next chapter: Chapter 10 – Sound Waves: Characteristics and Applications
See all chapters: MCQ Questions for Class 9 Science – All 13 Chapters
