Each MCQ has 4 options + correct answer.
Useful for Class 9 / DAV / CBSE exams & practice tests.
MCQs (1–20): Bohr’s Model of Atom
1. Who proposed the Bohr’s model of atom?
A. Rutherford
B. J.J. Thomson
C. Niels Bohr
D. Chadwick
Ans: C
2. In which year was Bohr’s model proposed?
A. 1905
B. 1913
C. 1922
D. 1932
Ans: B
3. According to Bohr, electrons revolve in:
A. Random paths
B. Elliptical orbits
C. Discrete circular orbits
D. Zig-zag paths
Ans: C
4. The special orbits of electrons are called:
A. Valence shells
B. Energy levels
C. Atomic layers
D. Rings
Ans: B
5. While revolving in permitted orbits, electrons:
A. Absorb energy
B. Lose energy
C. Radiate energy
D. Do not radiate energy
Ans: D
6. Energy levels are represented by:
A. Letters only
B. Numbers only
C. K, L, M, N or n = 1,2,3,4
D. Symbols only
Ans: C
7. Which shell is closest to the nucleus?
A. L
B. M
C. K
D. N
Ans: C
8. Value of n for K-shell is:
A. 0
B. 1
C. 2
D. 3
Ans: B
9. Bohr received Nobel Prize in:
A. 1916
B. 1922
C. 1932
D. 1945
Ans: B
10. Bohr was born in:
A. Germany
B. France
C. Denmark
D. England
Ans: C
11. The nucleus is present at the:
A. Edge of atom
B. Center of atom
C. Outside atom
D. Random place
Ans: B
12. Energy levels are also called:
A. Charges
B. Valencies
C. Orbits or shells
D. Nucleons
Ans: C
13. Which shell has maximum energy?
A. K
B. L
C. M
D. Outermost shell
Ans: D
14. Which shell is denoted by n = 3?
A. K
B. L
C. M
D. N
Ans: C
15. Bohr’s model explained:
A. Neutron discovery
B. Atomic stability
C. Chemical bonding
D. Nuclear fission
Ans: B
16. Electrons move around nucleus due to:
A. Magnetic force
B. Electrostatic force
C. Gravitational force
D. Nuclear force
Ans: B
17. Which scientist objected to Rutherford’s model?
A. Chadwick
B. Bohr
C. Dalton
D. Goldstein
Ans: B
18. Orbits in Bohr’s model are:
A. Continuous
B. Discrete
C. Overlapping
D. Random
Ans: B
19. Energy of electrons increases as distance from nucleus:
A. Decreases
B. Remains same
C. Increases
D. Becomes zero
Ans: C
20. Bohr’s model is applicable mainly to:
A. All atoms
B. Hydrogen atom
C. Heavy atoms
D. Molecules
Ans: B
MCQs (21–40): Electron Distribution & Shell Capacity
21. Maximum electrons in a shell is given by:
A. n²
B. 2n
C. 2n²
D. n³
Ans: C
22. Maximum electrons in K-shell:
A. 4
B. 6
C. 8
D. 2
Ans: D
23. Maximum electrons in L-shell:
A. 2
B. 4
C. 8
D. 18
Ans: C
24. Maximum electrons in M-shell:
A. 8
B. 18
C. 32
D. 2
Ans: B
25. Maximum electrons in N-shell:
A. 8
B. 18
C. 32
D. 50
Ans: C
26. Outermost shell can have maximum:
A. 2
B. 4
C. 6
D. 8
Ans: D
27. Electrons fill shells in:
A. Random order
B. Reverse order
C. Step-wise manner
D. Outermost first
Ans: C
28. Inner shells must be filled before:
A. Proton entry
B. Neutron entry
C. Outer shells
D. Valency calculation
Ans: C
29. Which shell fills first?
A. L
B. M
C. N
D. K
Ans: D
30. Electron distribution rule is given by:
A. Dalton
B. Bohr only
C. Bohr and Bury
D. Rutherford
Ans: C
31. Number of shells in sodium atom:
A. 1
B. 2
C. 3
D. 4
Ans: C
32. Electronic configuration of neon:
A. 2,6
B. 2,7
C. 2,8
D. 2,8,1
Ans: C
33. Atom with completely filled outer shell is:
A. Reactive
B. Inert
C. Radioactive
D. Unstable
Ans: B
34. Noble gases show:
A. High reactivity
B. Zero valency
C. High valency
D. Ionic bonding
Ans: B
35. Electronic configuration of magnesium:
A. 2,8,1
B. 2,8,2
C. 2,6
D. 2,7
Ans: B
36. Which element has 3 shells?
A. Oxygen
B. Nitrogen
C. Sodium
D. Neon
Ans: C
37. Which shell is valence shell?
A. Innermost
B. Middle
C. Outermost
D. All shells
Ans: C
38. Valence electrons decide:
A. Mass
B. Atomic number
C. Chemical properties
D. Isotopes
Ans: C
39. Which element has configuration 2,8,7?
A. Sulphur
B. Chlorine
C. Fluorine
D. Oxygen
Ans: B
40. Electronic configuration of aluminium:
A. 2,8,1
B. 2,8,2
C. 2,8,3
D. 2,7,4
Ans: C
MCQs (41–60): Valency
41. Valency is the:
A. Atomic mass
B. Combining capacity
C. Atomic number
D. Charge
Ans: B
42. Valence electrons are present in:
A. Nucleus
B. Innermost shell
C. Outermost shell
D. All shells
Ans: C
43. Valency of hydrogen is:
A. 0
B. 1
C. 2
D. 8
Ans: B
44. Valency of helium is:
A. 2
B. 1
C. 0
D. 8
Ans: C
45. Valency of oxygen is:
A. 6
B. 2
C. 8
D. 4
Ans: B
46. Valency of nitrogen is:
A. 3
B. 5
C. 7
D. 8
Ans: A
47. Valency of sodium is:
A. 2
B. 1
C. 3
D. 8
Ans: B
48. Valency of magnesium is:
A. 1
B. 2
C. 3
D. 4
Ans: B
49. Valency of aluminium is:
A. 1
B. 2
C. 3
D. 4
Ans: C
50. Valency of chlorine is:
A. 7
B. 1
C. 5
D. 3
Ans: B
51. Valency of sulphur is:
A. 6
B. 2
C. 4
D. 8
Ans: B
52. Noble gases have valency:
A. 1
B. 2
C. 8
D. 0
Ans: D
53. If valence electrons ≤ 4, valency =
A. 8 – electrons
B. Number of electrons
C. 2 × electrons
D. Zero
Ans: B
54. If valence electrons > 4, valency =
A. Number of electrons
B. 8 – valence electrons
C. Double electrons
D. Zero
Ans: B
55. Fluorine has valency:
A. 7
B. 1
C. 2
D. 8
Ans: B
56. Which element has valency 4?
A. Oxygen
B. Carbon
C. Nitrogen
D. Sodium
Ans: B
57. Valency helps in formation of:
A. Isotopes
B. Ions
C. Molecules
D. Neutrons
Ans: C
58. Valency depends on:
A. Neutrons
B. Protons
C. Valence electrons
D. Mass number
Ans: C
59. Valency of silicon is:
A. 2
B. 3
C. 4
D. 5
Ans: C
60. Which element has valency zero?
A. Neon
B. Sodium
C. Magnesium
D. Chlorine
Ans: A
MCQs (61–80): Atomic Number, Mass Number
61. Atomic number is denoted by:
A. A
B. N
C. Z
D. M
Ans: C
62. Atomic number equals number of:
A. Neutrons
B. Electrons + protons
C. Protons
D. Nucleons
Ans: C
63. Mass number equals:
A. Protons only
B. Neutrons only
C. Protons + neutrons
D. Electrons + protons
Ans: C
64. Protons and neutrons are together called:
A. Electrons
B. Ions
C. Nucleons
D. Isotopes
Ans: C
65. Atomic number of carbon is:
A. 12
B. 6
C. 14
D. 8
Ans: B
66. Mass number of carbon-12 is:
A. 6
B. 12
C. 14
D. 18
Ans: B
67. If Z = 8, element is:
A. Nitrogen
B. Oxygen
C. Carbon
D. Neon
Ans: B
68. Number of neutrons =
A. A – Z
B. Z – A
C. A + Z
D. A × Z
Ans: A
69. Nitrogen is written as:
A. ¹⁴₇N
B. ¹²₆C
C. ¹⁶₈O
D. ¹H
Ans: A
70. Atomic mass of aluminium is:
A. 13 u
B. 26 u
C. 27 u
D. 28 u
Ans: C
71. Hydrogen has number of protons:
A. 0
B. 1
C. 2
D. 3
Ans: B
72. Atomic number identifies:
A. Isotope
B. Element
C. Molecule
D. Compound
Ans: B
73. Neutrons are present in:
A. Nucleus
B. Orbits
C. Shells
D. Valence shell
Ans: A
74. Electron mass is:
A. Very high
B. Equal to proton
C. Negligible
D. Maximum
Ans: C
75. Atomic number of neon is:
A. 8
B. 9
C. 10
D. 11
Ans: C
76. Which particle has no charge?
A. Proton
B. Electron
C. Neutron
D. Ion
Ans: C
77. Charge on proton is:
A. Negative
B. Neutral
C. Positive
D. Variable
Ans: C
78. Atomic mass depends mainly on:
A. Electrons
B. Protons
C. Neutrons
D. Protons + neutrons
Ans: D
79. Atomic number of magnesium is:
A. 10
B. 11
C. 12
D. 13
Ans: C
80. Atomic mass unit is written as:
A. am
B. u
C. kg
D. g
Ans: B
MCQs (81–100): Isotopes & Isobars
81. Isotopes have same:
A. Mass number
B. Atomic number
C. Neutrons
D. Valency
Ans: B
82. Isotopes differ in:
A. Protons
B. Electrons
C. Neutrons
D. Atomic number
Ans: C
83. Three isotopes of hydrogen are:
A. H, He, Li
B. Protium, Deuterium, Tritium
C. H¹, H², H⁴
D. H, D, He
Ans: B
84. Atomic number of all hydrogen isotopes is:
A. 0
B. 1
C. 2
D. 3
Ans: B
85. Deuterium is written as:
A. ¹H
B. ²H
C. ³H
D. ⁴H
Ans: B
86. Tritium has mass number:
A. 1
B. 2
C. 3
D. 4
Ans: C
87. Isobars have same:
A. Atomic number
B. Mass number
C. Protons
D. Electrons
Ans: B
88. Isobars differ in:
A. Mass number
B. Neutrons
C. Atomic number
D. Electrons only
Ans: C
89. Example of isobars:
A. H and D
B. C-12 and C-14
C. Ca-40 and Ar-40
D. O-16 and S-16
Ans: C
90. Chlorine occurs naturally as:
A. One isotope
B. Two isotopes
C. Three isotopes
D. Four isotopes
Ans: B
91. Isotopes have:
A. Same chemical properties
B. Same physical properties
C. Different chemical properties
D. No properties
Ans: A
92. Average atomic mass of chlorine is:
A. 35
B. 36
C. 35.5
D. 37
Ans: C
93. Isotope of uranium is used as:
A. Medicine
B. Fertilizer
C. Nuclear fuel
D. Coolant
Ans: C
94. Cobalt isotope is used in:
A. Agriculture
B. Cancer treatment
C. Cooking
D. Photography
Ans: B
95. Iodine isotope is used in treatment of:
A. Cancer
B. Goitre
C. Diabetes
D. TB
Ans: B
96. Physical properties of isotopes are:
A. Same
B. Similar
C. Different
D. Identical
Ans: C
97. Chemical properties depend on:
A. Neutrons
B. Mass number
C. Atomic number
D. Nuclear mass
Ans: C
98. Which isotope has no neutrons?
A. Deuterium
B. Tritium
C. Protium
D. Carbon
Ans: C
99. Number of neutrons in C-14:
A. 6
B. 7
C. 8
D. 14
Ans: C
100. Which statement is correct?
A. Isotopes have different atomic numbers
B. Isobars have same atomic number
C. Isotopes have same atomic number
D. Isobars have same chemical properties
Ans: C
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