Can you clarify degrees of freedom for me : LUSENET : UR General Chemistry : One Thread

My current understanding of degrees of freedom is that there is one degree of freedom per direction movement (ie vibrational, translational, and rotational). Monatomic atoms have translational (temperature controlled)energy and their vibrational and rotational are negligible so KE = 3/2R and degrees freedom = 1. How do we calculate the degrees of freedom for complex molecules??

-- Anonymous, February 05, 2000


You were partially correct. Their are translational degree's of freedom as well as rotational and vibrational. So for every molecule there are 3 translational dregrees of freedom (x,y,z). For a monatomc molecule there is no rotational (assume a spherical shape) or vibrational degree's of freedom. This means that a monatomic molecule has 3 degree's of freedom total. When you add another atom and have a diatomic molecule, you have a linear molecule. So now in addition to the 3 translational degree's or freedom we also have rotational and vibrational degree's of freedom. As you add more and more atoms, making the molecule more complex, we add more degree's of freedom. The long and the short of it is this:

Total degree's of freedom = 3N; where N is the number of atoms in the molecule.

If you would like to understand more about the vibrational and rotational degree's of freedom feel free to ask. I think this should answer your question.

-- Anonymous, February 06, 2000

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