Periodic table Pauling electronegativities

Periodic table of electronegativity using the Pauling scale... 

Figure 1 Three electronegativity scales (Pauling units) for the second, third, fourth, and fifth rows of the periodic table. - - - Pauling, ----- A R CE...

Electronegativities, which have no units, are estimated by using combinations of atomic and molecular properties. The American chemist Linus Pauling developed one commonly used set of electronegativities. The periodic table shown in Eigure 9 7 presents these values. Modem X-ray techniques can measure the electron density distributions of chemical bonds. The distributions obtained in this way agree with those predicted from estimated electronegativities. 

We have shown19 that there are separate but nearly parallel linear relationships between the methyl deviations, 6(CH3—Z), of methyl substituted species CH3—Z and the electronegativity of the atom in Z bonded to carbon for functionality in the second row of the periodic table (Z = —OH, —NH2, —CH3, —B<) and in the third row of the periodic table (Z = —Cl, —SH, —Al<). If the methyl deviations for CII3B1 and (CH3)4Ge, both containing fourth-row atoms, are now calculated and the results plotted versus the Pauling electronegativity, the two new points fall on the line established by the third-row series (Figure 1). 

While fluorine is the most electronegative element (4.0 on Pauling s scale) and therefore the most powerful oxidiser, pyrotechnically important elements also rate highly e.g. nitrogen (3.0), chlorine (3.0) and oxygen (3.5) on the scale of electronegativity, which also depends on the position of the element in the Periodic Table. 

Figure 10-11 Pauling electronegativities of elements. The dashed lines connect elements in particular vertical columns of the periodic table.

Though neighbors on the periodic table of the elements with similar sizes, boron and carbon have some conspicuous electronic differences. The comparison of Pauling electronegativities (B 2.0 C 2.5) corroborates the chemical behavior of boron as a Lewis acid whereas carbon can behave as either a Lewis acid (as in carbonyls or carboxylic acids) or a Lewis base (as in hydrocarbons). Since both elements have small atomic radii (single bond... 

Fig. 1. The periodic table of noble metals (in the solid frame) and their neighbouring elements including Pauling electronegativities. The so-called pseudo-noble metals appear in the dashed frames...

Electronegativity is the ability of an atom (in a bond) to attract the electron density more than the other atom(s). Electronegativity increases from left to right and from the bottom to the top of the periodic table. Thus, fluorine (F) is the most electronegative element of the periodic table, with the maximum value of 4.0 in the Pauling scale of electronegativity. Metals are electropositive. See Lesson 11 for more on electronegativity. 

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