Periodic Compounds: Syntheses at High Pressures and Temperatures

A new class of compounds, called "periodic compounds," identified by the selection rule G = Sigmad(i)e(i)/Sigmad(i), where G assumes the integral values 1, 2, 3, . . . corresponding to the periodic table groups I, II, III, . . ., is discussed. The number of bonding electrons contributed by an atom of kind i is designated e(i), and d(i) gives the number, per formula weight, of atoms of this kind. Both e(i) and d(i) assume integral values. Periodic compounds consist of symmetrical and unsymmetrical types. The recent synthesis of the unsymmetrical periodic compound B(2)O, an isoelectronic analog of carbon, suggests that many more unsymmetrical types may be amenable to synthesis, particularly by high-pressure and high-temperature techniques.