Molecular orbital theory triatomic molecules

The application of molecular orbital theory to triatomic molecules, their bond lengths and strengths... 

The extension of molecular orbital theory to triatomic molecules is a major part of this chapter. It gives a very satisfactory description of the shapes and the bonding of molecules in general, and is consistent with observations of photoelectron and electronic absorption spectra. It is not possible for the VSEPR theory to explain these latter observations. 

The same principles that we have used for the description of diatomic molecules will now be used in a description of the electronic structures of triatomic molecules. However, let it be clear that in using molecular-orbital theory with any hope of success, we first have to know the molecular geometry. Only in very rare cases is it possible from qualitative molecular-orbital considerations to predict the geometry of a given molecule. Usually this can only be discussed after a thorough calculation has been carried out. 

In this section, we first discuss the bonding in two linear triatomic molecules BeH2 with only a bonds and C02 with both a and n bonds. Then we go on to treat other polyatomic molecules with the hybridization theory. Next we discuss the derivation of a self-consistent set of covalent radii for the atoms. Finally, we study the bonding and reactivity of conjugated polyenes by applying Hiickel molecular orbital theory. 

The simple molecular orbital theory of bonding in homonuclear diatomic molecules can be used to estimate the electron affinities of clusters. In these cases, there can be different geometries. The Cn clusters have been studied most extensively. In the case of the triatomic molecules, there are now two distances and one angle that... 

Chapter 4 Molecular orbital theory the ligand group orbital approach and application to triatomic molecules 107... 

This simple MO pictnre for ozone can also be employed to describe the bonding in other bent triatomic molecnles of second-row elements, such as NO2. Example 4.7 applies molecular orbital theory to CO2, a linear second-row triatomic molecule. 

A number of triatomic radicals can form dimers whose geometries have been well-characterized. A study of the electronic structures of these dimers can illustrate aspects of qualitative valence-bond and molecular orbital theory for electron-rich polyatomic molecules, and interconnections between these theories can be demonstrated. Dinitrogen tetroxide is a molecule par excellence that may be used for these purposes, and here we shall give primary consideration to its electronic structure and bond properties. 

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