Question

Why do homonuclear diatomic molecules not show ir spectra?

Answer 1

Answer:

homonuclear diatomic molecule like H2, O2, N2 etc. which have only stretching motion/ vibrations and no bending motion/vibrations, the dipole moment does not change during vibration. Hence these molecules do not give vibration spectra i.e. they are said to be infrared-inactive.

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Answer 2

Answer:

To show a vibrational spectrum , a diatomic molecule must have a dipole moment that varies with extension . So homonuclear diatomic molecules do not undergo electric -dipole vibrational transitions . So a homonuclear diatomic molecule doesn't show purely vibrational Spectra .