Practice question

Infrared inactivity stems from selection rule requiring change in dipole moment during vibration. Oxygen O2 and nitrogen N2 are homonuclear diatomics with identical electronegativities, so electron distribution remains symmetric, yielding zero permanent dipole. Stretching motion preserves symmetry, so instantaneous dipole stays zero, no coupling to infrared electromagnetic field occurs, preventing absorption despite high bond energy. Low frequency or heavy mass shifts position but does not cause inactivity; nonpolar bond description is vague. Raman spectroscopy detects these gases via polarizability modulation, complementing infrared for atmospheric analysis and greenhouse effect studies.