Electronegativity, described by Linus Pauling described as “The power of an atom in a molecule to attract electrons to itself” (Pauling in The nature of the chemical bond, 3rd edn, Cornell University Press, Ithaca, p 88, 1960), is used to predict bond polarity. There are dozens of methods for empirically quantifying electronegativity including: the original thermochemical technique (Pauling in J Am Chem Soc 54:3570–3582, 1932), numerical averaging of the ionisation potential and electron affinity (Mulliken in J Chem Phys 2:782–784, 1934), (...) effective nuclear charge and covalent radius analysis (Sanderson in J Chem Phys 23:2467, 1955) and the averaged successive ionisation energies of an element’s valence electrons (Martynov and Batsanov in Zhurnal Neorganicheskoi Khimii 5:3171–3175, 1980), etc. Indeed, there are such strong correlations between numerous atomic parameters—physical and chemical—that the term “electronegativity” integrates them into a single dimensionless number between 0.78 and 4.00 that can be used to predict/describe/model much of an element’s physical character and chemical behaviour. The design of the common and popular medium form of the periodic table is in large part determined by four quantum numbers and four associated rules. However, adding electronegativity completes the construction so that it displays the multi-parameter periodic law operating in two dimensions, down the groups and across the periods, with minimal ambiguity. (shrink)