[Plumbum]

Hi there

I have a question to the symmetry and the point groups.

I'm not quite sure to determine what kind of symmetry a molecule has and to which point gruoup it belongs.
I read that certain structures have certain point groups, that means that linear molecule would have the point group Dooh ?

Would that be correct?
Thank u

[Corribus]

D_∞h is one of the point groups for linear molecules. You can think about symmetry to determine how many point groups there should be. For instance, do CO₂ and CO have the same symmetry? If not, then they both can't be in the same point group. Therefore there has to be more than one point group for linear molecules.

[Plumbum]

Is it somehow defined which structure ( trigonal planar , linear etc. ) belongs to which point groups? Like trigonal planar would alaways be C1 and Dooh ( just example!!)

[Corribus]

The structure can narrow down the number possible point groups - for example, a tetrahedral molecule can never be D_4h, because the "4" implies a 4-fold rotational axis and the "h" implies a reflection plane perpendicular to the principle axis, neither of which is possible for a tetrahedral shape. However, the shape alone is not enough to determine the possible point group. Chloroform and methane are both essentially tetrahedral-like, but they have different point groups.

It sounds from your questions like you need to do some reading about point groups and molecular symmetry. Any introductory inorganic or physical chemistry textbook should be a good place to start.

[Plumbum]

yeah I actually did but I'll keep reading haha

I hate this topic  but thank u