Fixed Set of Atoms, and the FIEM

Extension of the equivaleiice relation of isomerism to ensembles of molecules leads to a unified theory for the relations between chemical systems. Previously, the potential importance of this extended equivalence relation to the interpretation of chemistry and systematic planning of chemical experiments seem to have been overlooked. 

There are two types of empirical formulas for EM, the gross empirical formula which indicates the total number of atoms that are contained in an EM, and the detailed empirical formula which represents the set of empirical formulas of the molecules that belong to the EM, 

Let be a given set of atoms. The empirical formula of A is the gross empirical formula of all isomeric EM that can be formed from A. The detailed empirical formula of an EM. 4) is a partition (Ai,..3, of A i.e., the 3( are pairwise disjoint and 3 = u.4i) such that each A is the empirical formula of a molecule. Thus, an EM(3) is any compound or collection of chemical species that can be formed from A using each atom belonging to A exactly once. Since isomeric molecules can differ constitutionally, there can be more than one EM(3) with a given detailed empirical formula. The constitutional formula of an EM(/1) is the set of formulas of all the molecules belonging to that EM(.4). 

An FIEM(4), the family of isomeric ensembles of molecules of A, is the set of all Thus, an FIEM is described simply by a gross empirical 

The constitutional chemistry of a set of atoms A is given by the FI EM (A). We elaborate this in more abstract terms  

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