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Quantum numbers and shapes of s, p and d orbitals: NEET MCQs with answers

85 questions on this topic of Atomic Structure (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. What is the orbital angular momentum of an electron present in a 4s orbital?

  1. h / (2π)
  2. 0
  3. √2 · h / (2π)
  4. √6 · h / (2π)
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Answer: (B) 0

Orbital angular momentum is given by √[l(l + 1)] · h / (2π). For an s orbital, the azimuthal quantum number l = 0, which makes the orbital angular momentum equal to zero.

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2. The number of angular nodes in a 6s orbital is:

  1. 1
  2. 5
  3. 6
  4. 0
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Answer: (D) 0

For 6s: n = 6, l = 0. Radial nodes = n − l − 1 = 5; angular nodes = l = 0; total = n − 1 = 5.

hard

3. Match List I (Orbital) with List II (Nodal characteristics) and choose the correct combination: List I: (A) 3s (B) 2pz (C) 3dxy (D) 3dz² List II: (1) 2 angular nodal planes (2) 2 conical nodal surfaces (3) 2 spherical nodes (4) 1 angular nodal plane (xy-plane)

  1. A-3, B-1, C-4, D-2
  2. A-3, B-4, C-1, D-2
  3. A-2, B-4, C-1, D-3
  4. A-4, B-3, C-2, D-1
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Answer: (B) A-3, B-4, C-1, D-2

A 3s orbital has n - l - 1 = 3 - 0 - 1 = 2 spherical (radial) nodes (A-3). The 2pz orbital has one angular nodal plane which is the xy-plane (B-4). The 3dxy orbital has two angular nodal planes, namely the xz and yz planes (C-1). The 3dz² orbital features two conical nodal surfaces rather than planar nodes (D-2).

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4. Which of the following statements is INCORRECT regarding the dz² orbital?

  1. It has two lobes pointing along the z-axis.
  2. It possesses a doughnut-shaped ring of high electron density in the xy-plane.
  3. It has two nodal planes passing through the origin.
  4. It has two conical nodal surfaces.
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Answer: (C) It has two nodal planes passing through the origin.

The dz² orbital does not possess planar nodal surfaces. Instead, it has two conical nodal surfaces inclined at specific angles to the z-axis. Its electron distribution consists of two lobes directed along the z-axis and an electron ring (torus) in the xy-plane.

easy

5. The maximum number of electrons in the shell with principal quantum number n = 1 is:

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

Each shell holds 2n² electrons: 2 × 1² = 2.

hard

6. Match List I with List II to identify the correct number of angular nodes and nodal surfaces: List I (Orbital): (A) 2pz (B) 3dz² (C) 3dx²-y² (D) 1s List II (Nodal feature): (I) Zero nodes of any kind (II) One planar node (xy plane) (III) Two planar nodal surfaces (IV) Two conical nodal surfaces Choose the correct answer from the options given below:

  1. A-II, B-IV, C-III, D-I
  2. A-II, B-III, C-IV, D-I
  3. A-I, B-IV, C-III, D-II
  4. A-III, B-II, C-IV, D-I
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Answer: (A) A-II, B-IV, C-III, D-I

(A) 2pz has 1 angular node, which is the xy planar node (II). (B) 3dz² has 2 conical nodal surfaces where electron density is zero (IV). (C) 3dx²-y² has 2 planar nodal surfaces at 45° to the axes (III). (D) 1s has n = 1, l = 0, meaning zero radial and zero angular nodes (I).

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7. What is the maximum number of electrons in an atom that can have the quantum numbers n = 3 and mₛ = +1/2?

  1. 18
  2. 3
  3. 6
  4. 9
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Answer: (D) 9

For n = 3, the total number of orbitals is n² = 3² = 9 orbitals (one 3s, three 3p, five 3d). Each orbital can hold at most one electron with spin mₛ = +1/2. Therefore, the maximum number of electrons sharing n = 3 and mₛ = +1/2 is 9.

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8. The number of total nodes in a 4p orbital is:

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

For 4p: n = 4, l = 1. Radial nodes = n − l − 1 = 2; angular nodes = l = 1; total = n − 1 = 3.

easy

9. Which of the following orbitals has two nodal planes lying specifically in the xz and yz planes?

  1. dxy
  2. dx²-y²
  3. dyz
  4. dxz
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Answer: (A) dxy

For a dxy orbital, the electron density is concentrated between the x and y axes. The probability density drops to zero where x = 0 (the yz plane) and where y = 0 (the xz plane), giving it two nodal planes: the xz plane and the yz plane.

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10. The number of angular nodes in a 4s orbital is:

  1. 4
  2. 1
  3. 0
  4. 3
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Answer: (C) 0

For 4s: n = 4, l = 0. Radial nodes = n − l − 1 = 3; angular nodes = l = 0; total = n − 1 = 3.

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11. The number of radial nodes in a 3d orbital is:

  1. 1
  2. 3
  3. 0
  4. 2
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Answer: (C) 0

For 3d: n = 3, l = 2. Radial nodes = n − l − 1 = 0; angular nodes = l = 2; total = n − 1 = 2.

easy

12. Which quantum number is primarily responsible for specifying the overall size and energy of an orbital in a hydrogen atom?

  1. Principal quantum number (n)
  2. Azimuthal quantum number (l)
  3. Magnetic quantum number (mₗ)
  4. Spin quantum number (mₛ)
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Answer: (A) Principal quantum number (n)

The principal quantum number n determines the main energy level or shell and primarily dictates the size and overall energy of the orbital in single-electron systems like hydrogen.

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