Van Arkel–Ketelaar triangle

A. Ketelaar) are triangles used for showing different compounds in varying degrees of ionic, metallic and covalent bonding.

Six years later, in 1947, Ketelaar developed van Arkel's idea by adding more compounds and placing bonds on different sides of the triangle.

Different compounds that obey the octet rule (sp-elements) and hydrogen can be placed on the triangle.

The bottom side (from metallic to covalent) contains compounds with varying degree of directionality in the bond.

The left side (from ionic to metallic) is meant for delocalized bonds with varying electronegativity difference.