Jnaanangkur The Learning Hub

🧪 MCQs on Structure of Atom

Target Audience: School Students | Competitive Exam Aspirants | Quiz Lovers

1. Who discovered the electron?

A) Rutherford
B) Niels Bohr
C) J.J. Thomson
D) Chadwick

Correct Answer: C) J.J. Thomson

Explanation: J.J. Thomson discovered electrons using cathode ray experiments.

2. Which subatomic particle has a positive charge?

A) Electron
B) Neutron
C) Proton
D) Photon

Correct Answer: C) Proton

Explanation: Protons carry a positive electric charge.

3. The nucleus of an atom contains:

A) Electrons only
B) Protons and neutrons
C) Neutrons only
D) Electrons and protons

Correct Answer: B) Protons and neutrons

Explanation: The nucleus is made up of protons and neutrons.

4. Which scientist proposed the nuclear model of atom?

A) Dalton
B) Bohr
C) Rutherford
D) Thomson

Correct Answer: C) Rutherford

Explanation: Rutherford proposed the nuclear model after the gold foil experiment.

5. The atomic number represents the number of:

A) Neutrons
B) Electrons and neutrons
C) Protons
D) Nucleons

Correct Answer: C) Protons

Explanation: Atomic number equals the number of protons in an atom.

6. Which particle has no charge?

A) Proton
B) Electron
C) Neutron
D) Positron

Correct Answer: C) Neutron

Explanation: Neutrons are electrically neutral.

7. The maximum number of electrons in K-shell is:

A) 2
B) 8
C) 18
D) 32

Correct Answer: A) 2

Explanation: K-shell (n=1) can hold a maximum of 2 electrons.

8. Which experiment led to the discovery of nucleus?

A) Cathode ray experiment
B) Oil drop experiment
C) Gold foil experiment
D) Canal ray experiment

Correct Answer: C) Gold foil experiment

Explanation: Rutherford’s gold foil experiment revealed the nucleus.

9. According to Bohr’s model, electrons revolve in:

A) Random paths
B) Circular orbits
C) Straight lines
D) Elliptical clouds

Correct Answer: B) Circular orbits

Explanation: Bohr proposed fixed circular orbits around the nucleus.

10. Which quantum number determines the shape of an orbital?

A) Principal quantum number
B) Azimuthal quantum number
C) Magnetic quantum number
D) Spin quantum number

Correct Answer: B) Azimuthal quantum number

Explanation: The azimuthal quantum number determines orbital shape.

11. The isotope of hydrogen having one neutron is:

A) Protium
B) Tritium
C) Deuterium
D) Positronium

Correct Answer: C) Deuterium

Explanation: Deuterium contains one proton and one neutron.

12. The mass number of an atom is equal to:

A) Protons + Electrons
B) Neutrons only
C) Protons + Neutrons
D) Electrons only

Correct Answer: C) Protons + Neutrons

Explanation: Mass number is the total number of nucleons.

13. Assertion (A): Electrons revolve around the nucleus.
Reason (R): Electrons are negatively charged particles.

A) Both A and R are true, and R explains A
B) Both A and R are true, but R does not explain A
C) A is true, but R is false
D) A is false, but R is true

Correct Answer: B) Both A and R are true, but R does not explain A

Explanation: Electrons revolve due to electrostatic attraction, not merely because they are negatively charged.

14. Which shell has the highest energy?

A) K-shell
B) L-shell
C) M-shell
D) N-shell

Correct Answer: D) N-shell

Explanation: Energy increases with distance from the nucleus.

15. The electronic configuration of oxygen (Atomic number 8) is:

A) 2, 6
B) 2, 8
C) 2, 4
D) 8, 2

Correct Answer: A) 2, 6

Explanation: Oxygen has 2 electrons in K-shell and 6 in L-shell.

16. Which scientist discovered the neutron?

A) Chadwick
B) Rutherford
C) Bohr
D) Dalton

Correct Answer: A) Chadwick

Explanation: James Chadwick discovered neutrons in 1932.

17. Match the Following:

1. Thomson → Plum pudding model
2. Rutherford → Nuclear model
3. Bohr → Planetary model

A) 1 and 2 only
B) 2 and 3 only
C) All are correct
D) Only 1 is correct

Correct Answer: C) All are correct

Explanation: Each scientist proposed the correctly matched atomic model.

18. Arrange the following atomic models chronologically:
1. Rutherford Model
2. Dalton Model
3. Thomson Model
4. Bohr Model

A) 2 → 3 → 1 → 4
B) 3 → 2 → 1 → 4
C) 2 → 1 → 3 → 4
D) 4 → 1 → 3 → 2

Correct Answer: A) 2 → 3 → 1 → 4

Explanation: Dalton came first, followed by Thomson, Rutherford, and Bohr.

19. Which principle states that exact position and momentum cannot be determined simultaneously?

A) Pauli Exclusion Principle
B) Aufbau Principle
C) Heisenberg Uncertainty Principle
D) Hund’s Rule

Correct Answer: C) Heisenberg Uncertainty Principle

Explanation: Heisenberg stated that position and momentum cannot both be measured accurately at the same time.

20. Which subatomic particle determines the chemical properties of an element?

A) Protons
B) Neutrons
C) Electrons
D) Nucleus

Correct Answer: C) Electrons

Explanation: Chemical properties depend on electron arrangement.

📘 Answer Key

1-C, 2-C, 3-B, 4-C, 5-C, 6-C, 7-A, 8-C, 9-B, 10-B,
11-C, 12-C, 13-B, 14-D, 15-A, 16-A, 17-C, 18-A, 19-C, 20-C

🎯 Total Score

20 Questions × 1 Mark = 20 Marks

🚀 Motivational Line

“Every atom of knowledge builds the universe of success. Keep learning and keep shining!”