This additional consistency reinforces the idea of a coherent and balanced structure within the periodic table, as represented by the eight-fold typology of metals and nonmetals. 16 Leach M 2013, Concerning electronegativity as a basic elemental property and why the Periodic table is usually represented in its medium form, Foundations of Chemistry, vol. 15, no. 1, pp. 13-29 17 Jensen WB 1986, Classification, symmetry, and the periodic table, Computers & Mathematics with Applications, vol. 12B (1-2), pp. 487-510 (496)