JEE Main · 2024 · Shift-IeasyBOND-097

The linear combination of atomic orbitals to form molecular orbitals takes place only when the combining atomic…

Chemical Bonding · Class 11 · JEE Main Previous Year Question

Question

The linear combination of atomic orbitals to form molecular orbitals takes place only when the combining atomic orbitals:

A. have the same energy B. have the minimum overlap C. have same symmetry about the molecular axis D. have different symmetry about the molecular axis

Options
  1. a

    A, B, C only

  2. b

    A and C only

  3. c

    B, C, D only

  4. d

    B and D only

Correct Answerb

A and C only

Detailed Solution

🧠 Linear Combination of Atomic Orbitals (LCAO) is effective only when the AOs meet specific conditions. Evaluate each:

A. Same energy: ✓ Essential — AOs with very different energies don't mix effectively.

B. Minimum overlap: ✗ Wrong — maximum overlap (not minimum) leads to effective bonding. Minimum overlap gives negligible interaction.

C. Same symmetry about the molecular axis: ✓ Essential — a σ-type AO cannot combine with a π-type AO due to symmetry mismatch (the bonding and antibonding contributions cancel).

D. Different energy: ✗ Directly contradicts condition A.

Answer: (b) A and C only\boxed{\text{Answer: (b) A and C only}}

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