Question

Among the molecules given below, identify those which are microwave
active. Justify your answer.
I2, HBr, CO2, CS2, NO

Answer 1

From the given options, only NO ( nitric oxide) and HBr ( Hydrogen bromide) are microwave active.

The main requirement for a molecule to be microwave active is dipole moment. A molecule should possess a permanent dipole moment for it to get a rotational spectrum and be microwave active.

Homonuclear molecules are not microwave active so I2 is inactive, CO2 and CS2 have net zero dipole moment so only HBr and NO qualify as microwave active molecules.