Question

\(N_2\) molecule does not show a pure vibrational (IR) spectrum because:

• A. Triple bond in \(N_2\) is very strong
• B. The dipole moment in \(N_2\) is zero
• C. Both (A) and (B)
• D. None of the above

Hint:

IR activity requires a change in dipole moment during vibration.

Answer 1

The Correct Option is B

Selection rule: d(mu)/dQ != 0 required. For N2, symmetry keeps mu=0 always, so d(mu)/dQ=0, forbidden. This is why N2 is Raman active but IR silent.

\[\boxed{\text{Zero dipole moment}}\]