What is "chemical space"

n. (context chemistry English) the set of all possible stable molecules

Chemical space is the space spanned by all possible (i.e. energetically stable) molecules and chemical compounds – that is, all stoichiometric combinations of electrons and atomic nuclei, in all possible topology isomers. Chemical reactions allow us to move in chemical space. The mapping between chemical space and molecular properties is often not unique, meaning that there can be very different molecules exhibiting very similar properties. Material design and drug discovery both involve the exploration of chemical space.

As of July 2009, there were 49,037,297 organic and inorganic substances registered with the Chemical Abstracts Service, indicating that they have been reported in the scientific literature. Systematic exploration of chemical space is possible by creating in silico databases of virtual molecules, which can be visualized by projecting multidimensional property space of molecules in lower dimensions.