What significance do theoretical concepts in chemistry have?

Chemical concepts are important to gain a qualitative understanding of chemistry. They are needed to find interesting questions to which experimental research as well as quantum-chemical investigations and computer simulations can contribute. We point out why chemical concepts should be seen as an important and from fundamental physical theories to a certain degree independent part of chemistry. An overview and analysis of some concepts - which are often introduced only in connection with special examples instead of a discussion for their own sake - are given. We take a closer look at some concepts to illustrate our assertions. An analysis of the stability of the cyclic (MoNL3)-trimer demonstrates how these concepts work and what they can tell us about this special case.