Distinguishing Atom Differences in a Molecular Graph Shape Index

The molecular shape index, previously described, has been extended to take into account the size differences among heteroatoms and carbon atoms in different valence states. In the algorithm for the shape index, 2 K, calculated as a function of the non‐hydrogen atom count, the count value of non‐C sp 3 atoms is modified by a term α. The value of α is derived from the covalent radius of an atom relative to the radius of C sp 3 . Several examples of the use of the atom‐specified shape index, 2 K α , in biological studies are presented.