Atom states in organic chemistry

The labeled molecular graph underlying a molecule with n atoms is a connected 

4-multigraph on n nodes, y e 94 , with the following additional properties The color 

An interaction of two atoms is called a covalent bond and is indicated in the molecular graph by lines. The number of lines is the bond multiplicity. A bond of multiplicity 1, visualized by one line is a single bond and indicates that the two atoms connected by the bond share two electrons. A double bond, represented in the drawing by two lines, has a bond of multiplicity 2 and indicates that four electrons are shared, etc. Other forms of interaction will be discussed in Section 2.4. Valence electrons that do not belong to a covalent bond form free electron pairs. A single valence electron is called an unpaired electron. 

For a bonded atom, the count of its electrons (engaged in covalent bonds, in free electron pairs and unpaired) may differ from the number of valence electrons of a free atom of the same element. The difference, if ciny, is the atom s charge. 

12 Definition (Atom state) An atom state is a quadruple Z = ( z,pz,qz,r2), where 

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