Pauling orbital electronegativity

Titanium dioxide differs from silica mainly in two respects (1) the Ti + ions are octahedrally coordinated in all three modifications of TiOji (2) the Ti—0 bond is more pronouncedly ionic than the Si—O bond. Using Pauling s electronegativity values (297), one calculates a 63% ionic character for the Ti—0 single bond versus 50% for Si—O. In SiOj, there is certainly some double bond character involving 3d orbitals of the Si atom, causing lowered ionic character. Therefore, characteristic differences should be expected regarding the surface chemistry. 

Pm is the electronic population of the atom A/ is the Pauling s electronegativity specific for the subshell (s-, p- etc.) to which the orbital i belongs, and Amk is the strength of the resonance interaction characteristic for the pair of atoms (chemical elements) M and K. Practical implementation goes further and sets... 

Following Townes and Dailey, we assume that the atomic orbital of the halogen has 15 % s-character when the halogen atom is bonded to an element which is more electropositive than the halogen atom by at least 0.25 in Pauling s electronegativity scale. 

The Gasteiger-Marsili approach uses the concept of the partial equalisation of orbital electronegativity. Electronegativity is a concept well known to chemists, being defined by Pauling as the power of an atom to attract electrons to itself. Mulliken subsequently defined the electronegativity of an atom A as the average of its ionisation potential and its electron affinity E ... 

Heterocyclic systems have played an important role in this historical development. In addition to pyridine and thiophene mentioned earlier, a third heterocyclic system with one heteroatom played a crucial part protonation and methylation of 4//-pyrone were found by J. N. Collie and T. Tickle in 1899 to occur at the exocyclic oxygen atom and not at the oxygen heteroatom, giving a first hint for the jr-electron sextet theory based on the these arguments.36 Therefore, F. Arndt, who proposed in 1924 a mesomeric structure for 4//-pyrone, should also be considered among the pioneers who contributed to the theory of the aromatic sextet.37 These ideas were later refined by Linus Pauling, whose valence bond theory (and the electronegativity, resonance and hybridization concepts) led to results similar to Hiickel s molecular orbital theory.38... 

A measure of the ability of an atom within a molecule to attract bonding electrons toward itselP . For a bond between two atoms of different electronegativities, the electron molecular orbital cloud is not symmetric, and the atom with the higher electronegativity attracts the larger proportion of the cloud. The most popular quantitative description was presented by Pauling, who based his scale on bond dissociation energies (measured in kcal per mol). 

Crystal radius, orbital radius, and ionization potential from Karplus and Porter (1970). Electronegativity from Pauling (1970). 

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