Class 9 Science Chapter 8 MCQ
Chapter 7: Journey Inside the Atom
50 MCQs | 5 Sets | Answers Included
Set 1: Introduction to Atoms and Thomson's Model
Questions 1–10
1. According to modern science, matter is ultimately composed of:
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Answer: (C) Atoms
2. Who suggested the concept of parmanus in ancient India?
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Answer: (A) Acharya Kanada
3. The Greek word "atomos" means:
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Answer: (B) Indivisible
4. John Dalton published his atomic theory in:
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Answer: (B) 1808
5. According to Dalton's original atomic theory, atoms were considered:
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Answer: (A) Indivisible particles
6. Which discovery showed that atoms are divisible?
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Answer: (B) Radioactivity
7. Who discovered the electron?
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Answer: (C) J. J. Thomson
8. Cathode rays consist of:
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Answer: (B) Negatively charged particles
9. What is the relative charge of an electron?
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Answer: (C) -1
10. Thomson's atomic model proposed that an atom contains:
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Answer: (A) A positive sphere with electrons embedded in it
Set 2: Rutherford's and Bohr's Atomic Models
Questions 11–20
11. Thomson's atomic model is commonly known as the:
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Answer: (B) Plum pudding model
12. Which experiment helped Rutherford discover the atomic nucleus?
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Answer: (B) Gold foil alpha-particle scattering experiment
13. Most alpha particles passed straight through Rutherford's gold foil because:
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Answer: (B) Most of an atom is empty space
14. The positive charge of an atom is concentrated mainly in its:
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Answer: (C) Nucleus
15. Which particle was identified by Rutherford as the positively charged constituent of the nucleus?
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Answer: (B) Proton
16. Who discovered the neutron in 1932?
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Answer: (A) James Chadwick
17. Which scientist proposed that electrons occupy fixed energy levels around the nucleus?
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Answer: (C) Bohr
18. According to Bohr's model, electrons occupy:
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Answer: (B) Fixed energy levels
19. In the shell notation of Bohr's model, the first shell is called:
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Answer: (A) K shell
20. When an electron moves from a higher energy level to a lower energy level, it:
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Answer: (B) Emits energy
Set 3: Subatomic Particles and Atomic Number
Questions 21–30
21. Which subatomic particle has a negative charge?
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Answer: (C) Electron
22. Which subatomic particle has a positive charge?
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Answer: (A) Proton
23. Which subatomic particle has no electric charge?
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Answer: (B) Neutron
24. The atomic number of an element is equal to its number of:
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Answer: (B) Protons
25. The mass number of an atom is the total number of:
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Answer: (A) Protons and neutrons
26. A neutral atom contains 11 protons. How many electrons does it have?
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Answer: (B) 11
27. An atom has 17 protons and 18 neutrons. Its mass number is:
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Answer: (C) 35
28. Most of the mass of an atom is concentrated in the:
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Answer: (B) Nucleus
29. The approximate relative mass of a proton is:
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Answer: (A) 1
30. An atom has atomic number 8 and mass number 16. How many neutrons does it have?
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Answer: (B) 8. Neutrons = mass number − atomic number = 16 − 8 = 8.
Set 4: Electronic Configuration and Valency
Questions 31–40
31. The maximum number of electrons in a shell is given by:
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Answer: (B) 2n²
32. What is the maximum number of electrons in the K shell?
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Answer: (A) 2
33. What is the maximum number of electrons in the L shell?
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Answer: (B) 8
34. What is the electronic configuration of sodium (atomic number 11)?
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Answer: (B) 2, 8, 1
35. What is the electronic configuration of oxygen (atomic number 8)?
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Answer: (A) 2, 6
36. The electrons present in the outermost shell of an atom are called:
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Answer: (C) Valence electrons
37. The valency of an element describes its combining capacity. What is the usual valency of magnesium with configuration 2, 8, 2?
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Answer: (B) 2
38. What is the usual valency of neon, which has a complete outer shell?
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Answer: (D) 0
39. An element has the electronic configuration 2, 8, 7. Its usual valency is:
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Answer: (A) 1
40. Which subatomic particle mainly determines the chemical behaviour of an atom?
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Answer: (A) Valence electrons
Set 5: Isotopes, Isobars and Applications
Questions 41–50
41. Atoms of the same element having the same atomic number but different mass numbers are called:
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Answer: (B) Isotopes
42. Atoms of different elements with the same mass number but different atomic numbers are called:
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Answer: (B) Isobars
43. Which pair represents isotopes of hydrogen?
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Answer: (A) Hydrogen-1 and Hydrogen-2
44. How many protons are present in every isotope of carbon?
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Answer: (B) 6
45. Carbon-12 and carbon-14 differ in their number of:
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Answer: (C) Neutrons
46. Which isotope is commonly used in radiocarbon dating of once-living materials?
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Answer: (C) Carbon-14
47. Which isotope of cobalt is used in some medical treatments, including radiotherapy?
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Answer: (A) Cobalt-60
48. A neutral atom has atomic number 12 and mass number 24. How many protons, electrons and neutrons does it contain?
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Answer: (A) 12 protons, 12 electrons and 12 neutrons
49. Two atoms have atomic numbers 17 and 17, but mass numbers 35 and 37. These atoms are:
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Answer: (B) Isotopes
50. Which statement about a neutral atom is correct?
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Answer: (B) It has equal numbers of protons and electrons