Interstellar Chemical Models
Interstellar clouds are harsh environments exposed to a energetic radiation, where the survival of molecules does not seem favorable. However, molecules are found in many different types of interstellar clouds. The study of molecules has a twofold interest. On the one hand, they serve as excellent tools to characterize the physical conditions prevailing in the clouds, and on the other, knowing how molecules are synthesized and why different environments host different types of molecules allows to understand the chemical evolution that matter experiences along the process in which stars and planets form. For this latter purpose, chemical models are an essential tool. This chapter provides the fundaments to build a chemical model of an interstellar cloud, describes which are the basic physical and chemical data needed to feed the model, and briefly discuss how these models assist in the interpretation of astronomical observations of molecules.