Adding Electronegativity Pauling

In the fourth paper of the series, Pauling (1932a) went a step further in the discussion of the partial ionic character of bonds. To the qualitative criterion for bond character presented before, he added a quantitative semiempirical criterion that enabled him to determine the approximate percentages of ionic and covalent character of bonds and then to map atoms in a scale of relative electronegativities. Pauling was thus able to suggest a viable alternative to the quantum mechanical treatment outlined in the former paper, which, as he pointed out before, was impossible to carry out except in the simplest cases. 

The oxidation state of any chemically bonded carbon may be assigned by adding —1 for each more electropositive atom and +1 for each more electronegative atom, and 0 for each carbon atom bonded directly to the carbon of interest (see Figure 10-11 for the Pauling electronegativity scale). That is,... 

Gordy s electronegativity differences are very nearly proportional to Pauling s (0.62 Gordy unit per Pauling unit) the two scales become almost identical if 0.80 is added to each of Gordy s values ... 

From theoretical considerations of bond formation in electrosorbates it was concluded that the underpotentially deposited metal ad-atoms can approximately be considered to be covalently bonded and nearly completely discharged if the difference in the Pauling s electronegativities of the substrate and adsorbed metal is I Ax I < 0.5 [6]. That means these systems have electrosorption valency i/z 1. Systems in which the electrosorption valency is equal to the ionic charge are those resulting from the UPD of heavy metal ions on noble and transition metal electrodes. 

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