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NEET Chemistry · Atomic Structure

Quantum numbers and shapes of orbitals

Taught in NCERT Class 11 Chemistry, Chapter 2: Structure of Atom.

3 verified questions: Easy 1 · Medium 2 · NEET level 0

Sample questions

Sample 1Easy

Which quantum number defines the three-dimensional shape of an orbital?

  1. A

    Principal quantum number

  2. B

    Magnetic orbital quantum number

  3. C

    Azimuthal quantum number

  4. D

    Electron spin quantum number

Show the answer
The answer is C.

The azimuthal (subsidiary or orbital angular momentum) quantum number l defines the shape of the orbital. The principal quantum number gives size and energy, and the magnetic quantum number gives spatial orientation.

  • A.

    The principal quantum number determines the size and largely the energy of the orbital.

  • B.

    The magnetic quantum number gives the orientation of the orbital, not its shape.

  • D.

    The spin quantum number refers to the orientation of the electron's spin, not to an orbital's shape.

NCERT: Class 11 Chemistry, Unit 2 (Structure of Atom), Quantum Numbers

Sample 2Medium

A boundary surface sketch of an atomic orbital shows four lobes of electron density lying in the xy plane, each lobe pointing between the x and y axes, with adjacent lobes of opposite sign and the xz and yz planes as nodal planes. Which description fits this orbital?

  1. A

    3d_xy, with l = 2 and one angular node

  2. B

    3d_xy, with l = 2 and two angular nodes

  3. C

    3d_x²–y², with l = 2 and two angular nodes

  4. D

    3p_x, with l = 1 and one angular node

Show the answer
The answer is B.

Four lobes lying between the x and y axes in the xy plane describe the d_xy orbital, for which l = 2. The number of angular nodes equals l, so there are two, the xz and yz planes.

  • A.

    The number of angular nodes equals l, so a d orbital (l = 2) has two angular nodes, here the xz and yz planes.

  • C.

    The lobes of 3d_x²–y² lie along the x and y axes, not between them.

  • D.

    A p orbital has only two lobes and one nodal plane.

NCERT: Class 11 Chemistry, Chapter 2

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