Do the scopes of the tags theoretical-chemistry, quantum-chemistry, and quantum-mechanics differ noticably enough in order to keep them all or can we merge two of them? IMHO, the quantum-mechanics tag is well suited for questions about the foundations and the more mathematical aspects of quantum theory that might have no direct connection to chemical systems, e.g. questions like this one, this one, or this one. That leaves theoretical-chemistry and quantum-chemistry for questions with a more chemistry-related background: But I think we don't need both of them and should merge quantum-chemistry into theoretical-chemistry since the latter one is a little more general. But I'm not working directly in the field of Theoretical Chemistry so there may be reasons for keeping the tags seperate.
I'm less certain about theory vs. computational chemistry. Perhaps that distinction can be maintained, since one is about the actual theory and one is about carrying things out on a computer.
But in the case of the two quantum tags, I see a lot of confusion and most questions with one are tagged in the other as well.
I'm bringing this back up, since I think we really should merge the tags.
However, the use of theoretical-chemistry is very vague and broad at the same time. It may deal with all sorts of different models and theories, at least judging from the scope of the questions, this is the use of this tag.
- orbitals: Bonding in diatomic C2, a carbon-carbon quadruple bond?
- solid state chemistry: Are chiral quasicrystals possible?
- kinetics: Definitions of autocatalysis
- nanotech: What does the charge distribution around a Stone-Wales defect look like?
- general terminology and their application: What does "reaction coordinate" mean? What does it mean when a reaction has TWO reaction coordinates?
Unfortunately the tag wiki is incomplete at best and the scope of these questions is just mentioned as:
For questions seeking generalised answers deduced from or composed of theories regarding the chemical reactions involved.
We also have a general without description and only 5 questions, while theo-chem has 55.
A lot of these questions also deal with models that would generally be considered quantum-chemistry or physical-chemistry. Appropriate retagging would be in order, as I think that theo-chem defines the scope of the questions best (in comparison within the range organic-chemistry, inorganic-chemistry, ...).
We might then want to go ahead and create a tag like the proposed general, but with a more meaningful name, like general-theories, chemical-models, ... (I cannot think of good ones right now). But yet again I am not sure if we actually need that.
If we clean up this tag, i.e. removing it from those questions that fit better in other categories, then I think merging would be very well applicable.
In general I think that conjunctional tagging is more appropriate in most cases: