 Solution

An ordinary molecular point group consists of the identity, proper rotations $C_n$, and, when present, reflections $\sigma$, inversion $i$, and improper rotations $S_n$. Each operation leaves the nuclear geometry and chemical labels equivalent, so only identical nuclei can be interchanged. Translations are not elements of the point group of a finite isolated molecule. The molecular symmetry operations determine how electronic and vibrational coordinates transform.