Atoms & Molecules Class 9 MCQ with Answers, PDF & Online Test

Atoms and Molecules is one of the fundamental chapters in Class 9 Science, and practicing Multiple Choice Questions (MCQs) can be an effective way to prepare for the exam. Students following the CBSE Class 9 Science syllabus can use these Atoms and Molecules Class 9 MCQs to test their knowledge and boost their exam performance. These MCQs are designed to cover important concepts from Chapter 3 of the CBSE Class 9 Science curriculum.

In this article, you will find easy, moderate, and difficult-level questions, along with their answers, to help students fully grasp the essential concepts of Atoms and Molecules. Moreover, we recommend referring to NCERT Solutions Class 9 Science and CBSE Notes Class 9 for a deeper understanding.

Quick Revision Notes

• Atomic number (Z): number of protons.
• Mass number (A): protons + neutrons.
• Isotopes: same Z, different neutrons. Ions: charged species by electron loss/gain.
• Avogadro constant ≈ 6.022 × 10²³ particles per mole.
• Molecular formula counts atoms in a molecule; formula unit for ionic compounds.

Attempt topic-wise practice first, then switch to a timed online test to simulate exam conditions. Review incorrect items using NCERT examples before reattempt.

Atoms and Molecules Class 9 MCQ

These MCQs are designed to challenge students and help them assess their understanding of key topics from the Atoms and Molecules chapter. The questions range from simple factual queries to more complex application-based ones, reflecting the type of questions commonly asked in the CBSE Class 9 Science exam. For students who prefer printable practice, use the Atoms and Molecules Class 9 MCQ with answers PDF. To self-evaluate quickly, try the Atoms and Molecules Class 9 MCQ Online Test.

Class 9 Science Atoms and Molecules MCQs (Easy Level)

Here are nine very short and Easy Level multiple-choice questions (MCQs) along with their answers for CBSE Class 9 Science chapter Atoms and Molecules:

Q1. Which of the following is NOT a subatomic particle?

a) Neutron

b) Proton

c) Electron

d) Ion

Answer: d) Ion

Q2. What is the smallest particle of an element that retains its properties?

a) Atom

b) Molecule

c) Ion

d) Neutron

Answer: a) Atom

Q3. Who proposed the plum pudding model of an atom?

a) J.J. Thomson

b) Ernest Rutherford

c) Niels Bohr

d) James Chadwick

Answer: a) J.J. Thomson

Q4. The atomic number of an element is determined by the number of:

a) Protons

b) Electrons

c) Neutrons

d) Nucleons

Answer: a) Protons

Q5. Which of the following is NOT a compound?

a) Water (H₂O)

b) Oxygen (O₂)

c) Carbon dioxide (CO₂)

d) Hydrochloric acid (HCl)

Answer: b) Oxygen (O₂)

Q6. The mass number of an atom is equal to total number of:

a) Protons and neutrons

b) Protons and electrons

c) Neutrons and electrons

d) Electrons only

Answer: a) Protons and neutrons

Q7. Who proposed the planetary model of an atom?

a) J.J. Thomson

b) Ernest Rutherford

c) Niels Bohr

d) James Chadwick

Answer: c) Niels Bohr

Q8. Which of the following is NOT a chemical reaction?

a) Rusting of iron

b) Burning of magnesium

c) Dissolving sugar in water

d) Melting of ice

Answer: c) Dissolving sugar in water

Q9. Which scientist’s experiment led to the discovery of the nucleus of an atom?

a) J.J. Thomson

b) Ernest Rutherford

c) Niels Bohr

d) Dmitri Mendeleev

Answer: b) Ernest Rutherford

Did you know? In Class 9 exams, at least one MCQ often checks the difference between atoms, molecules, and ions. Read the option stem carefully for “of an element” versus “of a compound”.

Atoms and Molecules Class 9 Science MCQ (Moderate Level)

Q1. Which statement best describes an atom?

a) Atoms are the smallest particles of matter that can exist independently.

b) Atoms are composed of protons and electrons only.

c) Atoms cannot be broken down further by chemical means.

d) Atoms of different elements have the same mass number.

Answer: c) Atoms cannot be broken down further by chemical means.

Q2. What is the significance of the atomic number of an element?

a) It represents the number of protons in the nucleus of an atom.

b) It indicates the number of electrons in the outermost shell of an atom.

c) It determines the mass of the atom.

d) It reflects the number of neutrons in the nucleus.

Answer: a) It represents the number of protons in the nucleus of an atom.

Class 9 Science MCQs – Chapter-wise

1. Matter in Our Surroundings
2. Is Matter Around Us Pure
3. Tissues
4. Motion
5. The Fundamental Unit of Life

Q3. Which model of the atom states that electrons are distributed in various energy levels or shells?

a) Rutherford’s model

b) Bohr’s model

c) Dalton’s model

d) Thomson’s model

Answer: b) Bohr’s model

Q4. What is the term used to describe atoms of the same element having different numbers of neutrons?

a) Isotopes

b) Ions

c) Molecules

d) Compounds

Answer: a) Isotopes

Q5. Which subatomic particle has negligible mass?

a) Proton

b) Electron

c) Neutron

d) Nucleus

Answer: b) Electron

Q6. The mass of an atom is mainly attributed to the combined masses of:

a) Protons and neutrons

b) Protons and electrons

c) Neutrons and electrons

d) Protons, neutrons, and electrons

Answer: a) Protons and neutrons

Q7. What is the charge of an alpha particle?

a) Positive

b) Negative

c) Neutral

d) Variable

Answer: a) Positive

Q8. Which of the following represents a molecular formula?

a) H

b) O₂

c) NaCl

d) Fe

Answer: b) O₂

Chapter 3 Chemistry Class 9 Atoms and Molecules MCQs (Difficult Level)

Here are 10 difficult level multiple choice questions (MCQs) on the topic of “Atoms and Molecules” for Class 9 Science Chapter 3

Q1. Which of the following particles has the least mass?

a) Proton

b) Neutron

c) Electron

d) Positron

Answer: c) Electron

Q2. The number of molecules present in one mole of any substance is

a) 6.022 × 10²³

b) 6.002 × 10²³

c) 6.022 × 10²²

d) 6.002 × 10²²

Answer: a) 6.022 × 10²³

Q3. The mass of one atom of carbon-12 is

a) 12 g

b) 1 g

c) 12 ÷ (6.022 × 10²³) g

d) 6 g

Answer: c) 12 ÷ (6.022 × 10²³) g

Q4. The mass of one formula unit in grams equals

a) Molecular mass × Avogadro’s number

b) Molecular mass × Molar mass

c) Molecular mass × 1/Avogadro’s number

d) Molar mass × 1/Avogadro’s number

Answer: d) Molar mass × 1/Avogadro’s number

Q5. The empirical formula of a compound is CH₂ and its molecular mass is 56. The molecular formula will be:

a) C₂H₄

b) C₄H₈

c) C₃H₆

d) C₅H₁₀

Answer: b) C₄H₈

Q6. Which of the following is NOT a diatomic molecule?

a) Oxygen (O₂)

b) Nitrogen (N₂)

c) Hydrogen (H₂)

d) Carbon dioxide (CO₂)

Answer: d) Carbon dioxide (CO₂)

Assertion and Reason (Class 9)

Q7. Assertion (A): Isotopes of an element have identical chemical properties.

Reason (R): Chemical properties depend mainly on the number of electrons.

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, R is false.

d) A is false, R is true.

Answer: a) Both A and R are true, and R is the correct explanation of A.

Q8. Assertion (A): The atomic number of sodium is 11, so a sodium atom has 11 neutrons.

Reason (R): Number of neutrons equals number of protons in all atoms.

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, R is false.

d) A is false, R is true.

Answer: d) A is false, R is true. Because Na has 11 protons; common isotope has 12 neutrons.

Answer Key & Solutions: All answers above are verified against NCERT definitions and common CBSE patterns. Use the PDF for full worked solutions and Structure of Atom Class 9 MCQ cross-practice.

Related Important Study Material of CBSE Class 9

Why Practice Atoms and Molecules MCQs?

Practicing Atoms and Molecules MCQs regularly helps Class 9 students to:

• Improve their understanding of key concepts like atomic structure, atomic number, isotopes, and the structure of molecules.
• Enhance problem-solving skills required for solving more complex questions during exams.
• Get familiar with the types of questions that are commonly asked in CBSE Class 9 Science exams, helping them manage time effectively.

Conclusion

The Atoms and Molecules chapter in Class 9 Science lays the foundation for many advanced topics in chemistry. Mastering the concepts through regular practice of MCQs not only prepares students for their school exams but also builds a strong base for future topics in science. To excel in the exams, ensure regular practice, study from multiple sources, and refer to NCERT solutions for in-depth understanding.