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Groups 13 to 18 electronic configurations: NEET MCQs with answers

48 questions on this topic of P-Block Elements (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. How many unpaired electrons are present in the ground-state electronic configuration of an uncharged atom of the chalcogen belonging to Period 4?

  1. 1
  2. 3
  3. 2
  4. 4
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Answer: (C) 2

The chalcogen in Period 4 is Selenium (Se, Z = 34). Its valence shell electronic configuration is 4s² 4p⁴. According to Hund's rule, a p⁴ subshell contains one fully paired orbital and two singly occupied orbitals, giving exactly 2 unpaired electrons.

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2. Consider the following statements regarding the electronic configuration of Group 18 elements: Statement I: All noble gases have the valence shell configuration ns² np⁶. Statement II: Radon has completely filled 4f, 5d, and 6p subshells in its ground state. In the light of the above statements, choose the correct option:

  1. Both Statement I and Statement II are correct.
  2. Statement I is correct but Statement II is incorrect.
  3. Statement I is incorrect but Statement II is correct.
  4. Both Statement I and Statement II are incorrect.
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Answer: (C) Statement I is incorrect but Statement II is correct.

Statement I is incorrect because Helium is a noble gas with the valence configuration 1s², not ns² np⁶. Statement II is correct because Radon (Z = 86) has the configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶, wherein the 4f, 5d, and 6p subshells are all completely filled.

hard

3. Given below are two statements: Statement I: In the ground state of a neutral bismuth atom (Z = 83), the penultimate shell contains a total of 18 electrons. Statement II: The filled 4f-subshell in bismuth belongs to its antepenultimate shell. In light of the above statements, choose the correct answer:

  1. Both Statement I and Statement II are true.
  2. Both Statement I and Statement II are false.
  3. Statement I is true but Statement II is false.
  4. Statement I is false but Statement II is true.
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Answer: (A) Both Statement I and Statement II are true.

The electronic configuration of Bismuth (Z = 83, n = 6) is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³. The penultimate shell is n = 5, containing 5s² 5p⁶ 5d¹⁰ = 18 electrons, so Statement I is true. The antepenultimate shell is n = 4, which contains the completely filled 4f¹⁴ subshell (along with 4s² 4p⁶ 4d¹⁰), so Statement II is also true.

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4. Given below are two statements regarding the electronic configurations of group 13 elements: Statement I: The electronic configuration of Gallium (Z = 31) contains completely filled 3d orbitals which shield the valence electrons less effectively than s and p orbitals. Statement II: Due to poor shielding by 3d electrons, the atomic radius of Gallium is slightly smaller than that of Aluminium. In light of the above statements, choose the correct answer:

  1. Both Statement I and Statement II are true.
  2. Both Statement I and Statement II are false.
  3. Statement I is true but Statement II is false.
  4. Statement I is false but Statement II is true.
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Answer: (A) Both Statement I and Statement II are true.

Gallium ([Ar] 3d¹⁰ 4s² 4p¹) contains ten intervening 3d electrons. Because d-orbitals have poor shielding power, the effective nuclear charge increases, causing Ga (135 pm) to have a slightly smaller atomic radius than Al (143 pm).

easy

5. Which of the following p-block elements has completely filled d-subshells in its penultimate shell but no f-electrons in its ground-state electronic configuration?

  1. Polonium (Z = 84)
  2. Lead (Z = 82)
  3. Bismuth (Z = 83)
  4. Indium (Z = 49)
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Answer: (D) Indium (Z = 49)

Indium (Z = 49) belongs to the 5th period with the electronic configuration [Kr] 4d¹⁰ 5s² 5p¹. Here, the penultimate shell (n = 4) has a completely filled 4d subshell and contains no 4f electrons, as 4f filling begins only in the 6th period.

hard

6. What is the total number of electrons having magnetic quantum number m = 0 in a neutral ground-state sulfur atom (Z = 16)?

  1. 9
  2. 8
  3. 6
  4. 10
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Answer: (A) 9

The electronic configuration of sulfur (Z = 16) is 1s² 2s² 2p⁶ 3s² 3p⁴. Subshells 1s, 2s, and 3s have m = 0 contributing 2 + 2 + 2 = 6 electrons. In 2p⁶, one orbital (m = 0) has 2 electrons. In 3p⁴, one orbital has 2 electrons and two orbitals have 1 electron each, so the m = 0 orbital contributes either 1 or 2 electrons (typically 1 or 2 depending on orientation, giving 9 total). Specifically: 1s(2) + 2s(2) + 2p(2) + 3s(2) + 3p(1) = 9.

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7. For a ground-state atom of Lead (Pb, Z = 82), what is the total number of electrons with orbital angular momentum quantum number l = 1?

  1. 18
  2. 24
  3. 30
  4. 26
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Answer: (D) 26

Electrons with l = 1 are p-electrons. Lead (Z = 82) has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p². Summing the p-electrons: 2p⁶ (6) + 3p⁶ (6) + 4p⁶ (6) + 5p⁶ (6) + 6p² (2) = 26 electrons.

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8. An element belongs to the 5th period and Group 15 of the periodic table. What is the total number of electrons with azimuthal quantum number l = 1 in this neutral ground-state atom?

  1. 15
  2. 21
  3. 18
  4. 24
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Answer: (B) 21

The element is Antimony (Sb, Z = 51). Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p³. Electrons with l = 1 are p-electrons. The p-subshells are 2p⁶ (6), 3p⁶ (6), 4p⁶ (6), and 5p³ (3). The total number of p-electrons is 6 + 6 + 6 + 3 = 21.

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9. An element belongs to Group 15 and Period 4 of the periodic table. What is the total number of electrons present in its penultimate shell (n = 3) in the neutral ground state?

  1. 8
  2. 18
  3. 15
  4. 5
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Answer: (B) 18

The element in Period 4, Group 15 is Arsenic (As, Z = 33). Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³. Its penultimate shell is n = 3, which contains 3s² 3p⁶ 3d¹⁰ = 2 + 6 + 10 = 18 electrons.

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10. What is the total number of fully filled orbitals in a ground-state Bromine atom (Z = 35)?

  1. 17
  2. 18
  3. 16
  4. 15
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Answer: (A) 17

The electronic configuration of Br (Z = 35) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵. The fully filled orbitals are: 1s (1), 2s (1), 2p (3), 3s (1), 3p (3), 3d (5), 4s (1), and 4p has 2 filled orbitals and 1 half-filled orbital. Total fully filled orbitals = 1 + 1 + 3 + 1 + 3 + 5 + 1 + 2 = 17.

easy

11. Which of the following p-block elements has the valence shell configuration (n-1)d¹⁰ ns² np⁵ in its ground state, where n = 4?

  1. Chlorine
  2. Iodine
  3. Bromine
  4. Astatine
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Answer: (C) Bromine

For n = 4, the configuration is 3d¹⁰ 4s² 4p⁵, which corresponds to Bromine (Z = 35) belonging to the 4th period and group 17.

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12. Given below are two statements: Statement I: Across period 3 from phosphorus to argon, the number of unpaired electrons in the ground state decreases monotonically. Statement II: The ground-state electronic configuration of phosphorus has three unpaired electrons, sulfur has two, chlorine has one, and argon has zero. In light of the above statements, choose the correct answer:

  1. Both Statement I and Statement II are true.
  2. Both Statement I and Statement II are false.
  3. Statement I is true but Statement II is false.
  4. Statement I is false but Statement II is true.
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Answer: (A) Both Statement I and Statement II are true.

Phosphorus (3p³) has 3 unpaired electrons, Sulfur (3p⁴) has 2 unpaired electrons, Chlorine (3p⁵) has 1 unpaired electron, and Argon (3p⁶) has 0 unpaired electrons. Therefore, from P to Ar, the number of unpaired electrons decreases monotonically (3 → 2 → 1 → 0), making both statements true.

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