VAN ARKEL-KETELAAR TRIANGLES

An equilateral triangle with vertices designated metallic (M), ionic ( I), and covalent (C) was introduced for pedagogical reasons many years ago by van Arkel and Ketelaar to qualitatively catalogue the types of chemical bonding organized by the Periodic Table. These triangles dis play a sequence of atoms from left to right (M to C) in the Periodic T able along one side and binary combinations of atoms along the other t wo sides (M-I and I-C), and we have systematically extended the inform ation content and usefulness. By the positioning of atom pair combinat ions according to the sum and difference of configuration energies, CE (the average ionization energy of the valence electrons of an atom). This permits division of the triangle into regions corresponding to me tallic, ionic, and covalent bonding and, in effect, quantifies the Per iodic Table. Very recently Professor Gordon D. Sproul of the Universit y of South Carolina, Beaufort, found literature references on several hundred binary compounds previously determined to be bound as metallic , ionic, or covalent compounds, and cleanly separated these into their known bonding categories by use of CE with plots which give essential ly the same dividing lines that we have derived theoretically.