Chapter 4 of class 9 science as per the NCERT syllabus is Structure Of The Atom which deals with Thomson’s Model of the Atom, Rutherford’s Model of the Atom, the Drawbacks of Rutherford’s Model, Bohr’s Model of the Atom, Discovery of Neutrons, Distribution of Electrons in Shells, Valency, Atomic Number and Mass Number, Isotopes, Isobars, etc.
Here, we have discussed 30 Multiple Choice Questions based on these topics of the chapter. These questions will help you to learn more about the chapter and test your knowledge.
For each question below, there are four options out of which only one option is correct. The correct answer to each question is given at the end for your reference.
MCQ on Class 9 Science Chapter 4
1. What was the major challenge scientists faced at the end of the 19th century?
A) Revealing the properties of electrons
B) Identifying the structure of protons
C) Revealing the structure of the atom and explaining its properties
D) Discovering the existence of neutrons
2. Who discovered the electron?
A) J.J. Thomson
B) E. Goldstein
C) Ernest Rutherford
D) Niels Bohr
3. What were the radiations discovered by E. Goldstein in a gas discharge called?
A) Alpha particles
B) Beta particles
C) Canal rays
D) Gamma rays
4. Which sub-atomic particle has a charge equal in magnitude but opposite in sign to that of the electron?
A) Proton
B) Neutron
C) Positron
D) Beta particle
5. What is the mass of a proton taken as?
A) 1 u
B) 2 u
C) 0 u
D) 1836 u
6. What was the name given to positively charged radiations discovered by E. Goldstein?
A) Beta particles
B) Gamma rays
C) Canal rays
D) Alpha particles
7. According to Thomson’s model, how are the electrons arranged within an atom?
A) Electrons are spread uniformly throughout the atom.
B) Electrons revolve around the nucleus in circular paths.
C) Electrons are embedded in a sphere of positive charge.
D) Electrons are confined to specific energy levels.
8. Who designed the alpha-particle scattering experiment?
A) J.J. Thomson
B) E. Goldstein
C) Ernest Rutherford
D) Niels Bohr
9. What was the unexpected result of Rutherford’s alpha-particle scattering experiment?
A) Most of the alpha particles were deflected by large angles.
B) Most of the alpha particles passed straight through the gold foil.
C) Alpha particles exhibited no deflection.
D) Alpha particles rebounded from the gold foil.
10. What did Rutherford conclude from his alpha-particle scattering experiment?
A) Atoms consist of a positively charged nucleus.
B) Atoms are mostly empty space.
C) Electrons are located in the nucleus.
D) Atoms have no nucleus.
11. According to Rutherford’s model of the atom, where is most of the mass of an atom located?
A) In the electrons
B) Spread uniformly throughout the atom
C) In the nucleus
D) In the empty space surrounding the nucleus
12. What was the major drawback of Rutherford’s model of the atom?
A) It failed to explain the stability of atoms.
B) It failed to account for the existence of neutrons.
C) It failed to describe the behavior of electrons.
D) It failed to explain the existence of energy levels.
13. How did Niels Bohr address the stability issue in Rutherford’s model?
A) By proposing that electrons revolve around the nucleus in circular orbits.
B) By suggesting that electrons are embedded in a sphere of positive charge.
C) By introducing the concept of energy levels in which electrons do not lose energy.
D) By stating that electrons have no mass.
14. Who discovered the neutron?
A) J.J. Thomson
B) Ernest Rutherford
C) Niels Bohr
D) James Chadwick
15. Which statement best describes the distribution of electrons in different orbits according to Bohr?
A) Electrons occupy all possible energy levels simultaneously.
B) Electrons are confined to specific energy levels called shells.
C) Electrons move randomly within the atom.
D) Electrons revolve around the nucleus in elliptical orbits.
16. What is the maximum number of electrons that can be accommodated in the first orbit of an atom?
A) 2
B) 6
C) 8
D) 18
17. What is the valency of an element with two electrons in its outermost shell?
A) 1
B) 2
C) 3
D) 4
18. How is the valency of an element with seven electrons in its outermost shell determined?
A) By adding 7 electrons to the octet
B) By subtracting 7 electrons from the octet
C) By sharing electrons with another atom
D) By gaining or losing electrons to achieve an octet
19. What is the atomic number of an element defined as?
A) The total number of protons and neutrons in the nucleus
B) The total number of neutrons in the nucleus
C) The total number of electrons in the atom
D) The total number of protons in the nucleus
20. What is the mass number of an atom defined as?
A) The total number of protons and electrons in the atom
B) The total number of electrons in the atom
C) The total number of protons and neutrons in the nucleus
D) The total number of neutrons in the nucleus
21. Which term refers to atoms of the same element with different mass numbers?
A) Isotopes
B) Isomers
C) Isobars
D) Isotones
22. What are atoms having the same mass number but different atomic numbers called?
A) Isotopes
B) Isomers
C) Isobars
D) Isotones
23. What is the average atomic mass of an element based on?
A) The mass of its most abundant isotope
B) The sum of the masses of all its isotopes
C) The ratio of protons to neutrons in its nucleus
D) The number of energy levels in its electron configuration
24. Which sub-atomic particle did J.J. Thomson discover?
A) Neutron
B) Proton
C) Electron
D) Positron
25. Who proposed that electrons revolve around the nucleus in circular orbits?
A) J.J. Thomson
B) Ernest Rutherford
C) Niels Bohr
D) E. Goldstein
26. What is the combining capacity of an atom called?
A) Atomic number
B) Valency
C) Mass number
D) Isotope
27. What did Rutherford’s alpha-particle scattering experiment conclude about the atom’s structure?
A) Atoms are mostly empty space.
B) Electrons are located in the nucleus.
C) Atoms have no nucleus.
D) Atoms consist of a positively charged nucleus.
28. Who discovered the presence of neutrons in the nucleus of an atom?
A) J.J. Thomson
B) Ernest Rutherford
C) Niels Bohr
D) James Chadwick
29. What is the maximum number of electrons that can be accommodated in the third orbit of an atom?
A) 2
B) 8
C) 18
D) 32
30. Which sub-atomic particle has no charge and a mass nearly equal to that of a proton?
A) Neutron
B) Electron
C) Positron
D) Beta particle
Correct Answers
Here is the list of correct answers to the above questions.
- C) Revealing the structure of the atom and explaining its properties
- A) J.J. Thomson
- C) Canal rays
- A) Proton
- A) 1 u
- C) Canal rays
- C) Electrons are embedded in a sphere of positive charge.
- C) Ernest Rutherford
- B) Most of the alpha particles passed straight through the gold foil.
- A) Atoms consist of a positively charged nucleus.
- C) In the nucleus
- A) It failed to explain the stability of atoms.
- B) By suggesting that electrons are embedded in a sphere of positive charge.
- D) James Chadwick
- B) Electrons are confined to specific energy levels called shells.
- A) 2
- A) 1
- B) By subtracting 7 electrons from the octet
- D) The total number of protons in the nucleus
- C) The total number of protons and neutrons in the nucleus
- A) Isotopes
- C) Isobars
- B) The sum of the masses of all its isotopes
- C) Electron
- C) Niels Bohr
- B) Valency
- A) Atoms are mostly empty space.
- D) James Chadwick
- C) 18
- A) Neutron
The Bottom Line
I hope these 30 MCQs on Structure Of The Atom of Class 9 Science Chapter 4 have helped you in your studies and preparation.
If you have any queries, or comments or find any mistake in the above questions, feel free to contact me in the comment section below.
I would love to hear from you.
Abdur Rohman is an Electrical Engineer from Charaideo, Assam, who wears multiple hats as a part-time teacher, blogger, entrepreneur, and digital marketer. Passionate about education, he founded The Assam School blog to provide free, comprehensive textbook solutions, MCQs (Multiple Choice Questions), and other academic content for students from Class V to XII.