What significance do theoretical concepts in chemistry have?

Chemical concepts are important to gain a qualitative understanding of chem istry. They are needed to find interesting questions to which experimental research as well as quantum-chemical investigations and computer simulation s can contribute. We point out why chemical concepts should be seen as an i mportant and from fundamental physical theories to a certain degree indepen dent part of chemistry. An overview and analysis of some concepts - which a re often introduced only in connection with special examples instead of a d iscussion for their own sake - are given. We take a closer look at some con cepts to illustrate our assertions. An analysis of the stability of the cyc lic (MoNL3)-trimer demonstrates how these concepts work and what they can t ell us about this special case.