Periodic table electronegativity variation

Nonmetals follow the general trends of atomic radii, ionization energy, and electron affinity. Radii increase to the left in any row and down any column on the periodic table. Ionization energies and electron affinities increase up any column and towards the right in any row on the periodic table. The noble gases do not have electron affinity values. Ionization energies are not very important for the nonmetals because they normally form anions. Variations appear whenever the nonmetal has a half-filled or filled subshell of electrons. The electronegativity... 

This section summarizes the variation, across the periods and down the groups of the Periodic Table, of (i) the ionization energies, (ii) the electron attachment energies (electron affinities), (iii) the atomic sizes and (iv) the electronegativity coefficients of the elements. 

Variation of electronegativities of representative elements across a given period of the periodic table. Elements of period 6 have electronegativities very similar to those of elements of period 5. For clarity, electronegativities of the elements of period 6 are not shown. 

Variation of electronegativities of transition metals across a given period of the periodic table. 

This attenuation of the electronegativity variation in the earlier columns of the Periodic Table is even more pronounced when S is compared with Se. A choice of selenium-containing ligands (20, 22, 23) have Xopt 0.05 to 0.1 unit below that of the corresponding sulphur-containing ligands. Before the work described in this review, the spectra of complexes of Se 2 were not known. 

Even without microscopic voids, charge and potential fluctuations are expected to result from variations in electronegativity which in turn are a consequence of spatial fluctuations in density and composition. Furthermore, the difference in electronegativity between the elements in the respective columns of the periodic table may cause a local charge transfer when isoelectronic elements are substituted even without a change in coordination. In crystalline material this electronegativity difference gives rise to isoelectronic donor centers (Thomas etal (1965)). 

Note that the values given in Table 1.4 are only approximate. The electronegativity of a particular element depends not only on its position in the Periodic Table, but also on its oxidation state. The electronegativity of Cu(I) in CugO, for example, is 1.8, whereas the electronegativity of Cu(II) in CuO is 2.0. In spite of these variations, electronegativity is still a useful guide to the distribution of electrons in a chemical bond. 

---