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Atomic Structure

99 MCQ questions with answers and explanations · page 3 of 4

Test yourself▶ 25 question test▶ 50 question test

Q51. What controls the orientation of molecular orbitals?

  1. Aazimuth quantum number
  2. Bspin quantum number
  3. Cmagnetic quantum number
  4. Dprincipal quantum number
Show answer & explanation

Answer: C) magnetic quantum number

Q52. When two electrons are in the same orbital, what happens to them?

  1. Asame rotation
  2. Breverse spin
  3. Csame or opposite spin
  4. Dno rotation
Show answer & explanation

Answer: B) reverse spin

Q53. The principle that "electrons do not pair up until the vacant orbital available for them is filled" is called-

  1. AHund's law
  2. BPauli's law
  3. CAufbau principle
  4. DHeisenberg's principle
Show answer & explanation

Answer: A) Hund's law

Q54. The uncertainty principle was formulated by-

  1. AEinstein
  2. BHeisenberg
  3. CRutherford
  4. DPaulie
Show answer & explanation

Answer: B) Heisenberg

Q55. "The position and velocity of small particles like electrons cannot be determined simultaneously" is the statement of-

  1. AHeisenberg's uncertainty principle
  2. BPauli's exclusion principle
  3. Cof the Aufbau principle
  4. DDe Broglie's idea of the wave nature of electrons
Show answer & explanation

Answer: A) Heisenberg's uncertainty principle

Q56. The chemical behaviour of an atom depends on its-

  1. Aon the number of protons in the nucleus
  2. Bon the number of neutrons in the nucleus
  3. CThe number of electrons revolving around the nucleus
  4. Don the number of nucleons in the nucleus
Show answer & explanation

Answer: C) The number of electrons revolving around the nucleus

Q57. When an electron moves from a higher orbit to a lower orbit, then-

  1. Aenergy is released
  2. BEnergy is absorbed.
  3. Cthe size of the atom decreases
  4. Dnone of these
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Answer: A) energy is released

Q58. Which one of the following pairs is a particle-antiparticle pair?

  1. Aelectron positron
  2. Bproton neutron
  3. Cphoton – electron
  4. DNeutron - Neutrino
Show answer & explanation

Answer: A) electron positron

Q59. The atomic number of a nucleus is Z and its mass number is M. What will be the number of neutrons in the nucleus?

  1. AM + Z
  2. BM-Z
  3. CM x Z
  4. DM ÷ Z
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Answer: B) M-Z

Q60. The number of electrons in an atom of atomic number Z and mass number A is

  1. AZ
  2. BA-Z
  3. CA
  4. DA-Z
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Answer: A) Z

Q61. The number of electrons and neutrons in an element is 18 and 20 respectively. The mass number of this element is-

  1. A22
  2. B2
  3. C38
  4. D20
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Answer: C) 38

Q62. An atom has 9 electrons, 9 protons, and 10 neutrons. Its mass number will be:

  1. A9
  2. B10
  3. C18
  4. D19
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Answer: D) 19

Q63. An atom of an element has 19 protons and 20 neutrons. Its mass number will be-

  1. A39
  2. B19
  3. C20
  4. D12
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Answer: A) 39

Q64. If an atom of an element has 2 protons, 2 neutrons and 2 electrons, then what will be the mass number of that element?

  1. A2
  2. B4
  3. C6
  4. D8
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Answer: B) 4

Q65. An atom has a mass number of 23 and an atomic number of 11. Find the number of protons.

  1. A23
  2. B22
  3. C12
  4. D11
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Answer: D) 11

Q66. The number of neutrons and protons in the nucleus of ₈₈Ra²²⁶ are respectively-

  1. A138 and 88
  2. B88 and 138
  3. C226 and 88
  4. D88 and 226
Show answer & explanation

Answer: A) 138 and 88

Q67. Carbon has an atomic number of 6 and an atomic weight of 12. How many protons are in its nucleus?

  1. A6
  2. B12
  3. C18
  4. D0
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Answer: A) 6

Q68. The atomic number of element A is 13. The number of valence electrons in it will be-

  1. A0
  2. B1
  3. C2
  4. D3
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Answer: D) 3

Q69. The nucleus of a chlorine atom of atomic number 17 and mass number 35 contains-

  1. A18 protons
  2. B18 neutrons
  3. C35 protons
  4. D35 neutrons
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Answer: B) 18 neutrons

Q70. What does the nucleus of a singly ionized carbon atom contain?

  1. A6 protons and 6 neutrons
  2. B5 protons and 6 neutrons
  3. C6 protons, 6 neutrons and 6 electrons
  4. D12 protons, 6 neutrons and 6 electrons
Show answer & explanation

Answer: A) 6 protons and 6 neutrons

Q71. The atomic number of sodium is 11 and its atomic mass is 23. The number of electrons, neutrons and protons in it will be respectively-

  1. A11, 11, 12
  2. B12, 11, 12
  3. C12, 12, 11
  4. D11, 12, 11
Show answer & explanation

Answer: D) 11, 12, 11

Q72. The atomic number of an element is 35 and it has 18 electrons, then the number of protons in it will be-

  1. A17
  2. B18
  3. C20
  4. D15
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Answer: A) 17

Q73. The number of electrons in ₁₉K⁴⁰ is-

  1. A18
  2. B19
  3. C20
  4. D40
Show answer & explanation

Answer: B) 19

Q74. The number of protons in the element ₉₂U²ᶾ⁵ is-

  1. A92
  2. B146
  3. C235
  4. D135
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Answer: A) 92

Q75. The number of neutrons in ₉₂U²ᶾ⁸ will be-

  1. A146
  2. B234
  3. C90
  4. D148
Show answer & explanation

Answer: A) 146

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