Mendeleev periodic table of atoms is one of the most important principles in
natural science. However, there is not such a thing for molecules. Here we propose
three periodic tables for diatomic molecules, triatomic molecules and AH3 tetratomic
molecules, respectively. The tables not only contain isolated molecules, but also the
“virtual” diatomic molecules in polyatomic molecules. The form of these molecular
periodic tables is analogous to that of Mendeleev periodic table. In the table, molecules
are classified and arranged by their group number G, which is the number of valence
electrons, and the periodic number P, which represents the size of molecules. Basic
molecular properties, including bond length, binding energy, force constant, ionization
potential, spin multiplicity, chemical reactivity, or bond angle, among others. change
periodically with the tables. This periodicity originates from the shell-like electronic
configurations of molecules. The periodic tables can be used to predict unknown
properties of molecules, to understand the role of virtual molecules in polyatomic
molecules, and to initiate new research fields such as the periodicity of aromatic
compounds, clusters, or nanoparticles.
Keywords: Bond angle, bond energy, chemical reactivity, diatomic molecules,
dissociation energy, ionization potential energy, molecular classification,
molecular periodic table, molecular properties, multiplicity, periodic change,
periodic table, periodicity, spectral term, triatomic molecules.
