(I) In case of monoatomic gas, such a helium, neon, organ, kripton, etc have translational degree of freedom.
If N= 1 and K = 0, then f= 3×1-0=3
(II) In case off diatomic gas, such a oxygen hydrogen, nitrogen, etc each molecule has two rotational degrees of freedom in addition to three translation degree of freedom.
Therefore f=5
(III) The gas like SO₂, H₂S, etc has three molecules i.e they are triatomic gases. In case of triatomic gases, f=7 for linear molecules and f=6 for non-linear molecules.