Natural resonance theory bond order

The NRT resonance weights, bond orders, and valencies are generally comparable to those of the older Pauling-Wheland theory (particularly for species of low ionicity) and can be used to rationalize chemical phenomena in a similar fashion. Pauling s classic, The Nature of the Chemical Bond, brilliantly illustrates such reasoning. 

Natural resonance theory (NRT) allows these conflicting pictures of the oxyan-ion electron distributions to be tested quantitatively.149 Table 3.36 compares the geometries, NRT bond orders, atomic charges, and d-orbital occupancies for a representative variety of first- and second-row XOm"+ species,... 

Discuss the nature of the bonding in the nitrite ion (NO2). Draw the possible Lewis resonance diagrams for this ion. Use the VSEPR theory to determine the steric numbeg the hybridization of the central nitrogen atom, and the geometry of the ion. Show how the use of resonance structures can be avoided by introducing a de-localized 77 MO. What bond order does the MO model predict for the N—O bonds in the nitrite ion ... 

We have already argued that discussions of bond strength should most naturally be given in terms of two-particle matrices. But before doing so it is worth looking briefly at earlier discussions in terms of the one-particle matrix. In Hiickel theory, where in (5) there are no terms g(ij), (6) shows that the energy involves only y hence a one-particle discussion is reasonable. The simplest example is the Coulson bond order, which is simply an off-diagonal element in the expansion of (9) in terms of atomic orbitals it is also the differential coefficient of (H) with respect to the appropriate resonance... 

L. Pauung (Pasadena) I should like to object to the use by Dr. Pople of the expression the presence of the structures in the hydrogen bond . I think that one must be careful to use expressions such as 4 the contribution of the structures. . in order that listeners should not be misled as to the nature of the theory of resonance. 

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