Question

The number of degrees of freedom for a rigid diatomic molecule is ____________.

• A. $3$
• B. $5$
• C. $6$
• D. $7$

Answer 1

The correct option is B $5$

Number of degree of freedom $d=3N-1$

where $N$ is the number of atoms in a molecules

In diatomic molecules, $N=2$

$⟹$ $d=3\left(2\right)-1=5$

Hence diatomic molecule has $5$ degrees of freedom ($3$ translational and $2$ rotational).