<P> As noted in the article on heat capacity, diatomic gases should have 7 degrees of freedom, but the lighter gases act as if they have only 5 . </P> <P> Thus the kinetic energy per kelvin (monatomic ideal gas) is: </P> <Ul> <Li> per mole: 12.47 J </Li> <Li> per molecule: 20.7 yJ = 129 μeV . </Li> </Ul> <Li> per mole: 12.47 J </Li>

Degree of freedom- kinetic theory of gases