Molecular Orbital Configurations

Answer. The ground molecular orbital configuration of the electrons in NO is (see also Section 7.2.1.2)... 

To derive the states arising from a molecular orbital configuration in a diatomic molecule see Sections 7.2.2 and 7.2.4. There are two states, and 11 /2, arising from this configuration and is the lower in energy and, therefore, the ground state. 

The molecular orbital configuration of N2 has been described in Section 7.2.1.1. The ground... 

Electron configurations for these molecules lead to a guideline for molecular orbital configurations based on average nuclear charge, average ... 

Further evidence that this is the correct energy level scheme to be used for C2 comes from the fact that the molecule is diamagnetic. The molecular orbital configurations for these molecules can be written as... 

After writing the molecular orbital configuration, the vector sums are obtained. For example, in H2 the two bonding electrons reside in a a orbital, and they are paired so S = + Vi + — Vi) = 0. As shown earlier, for a cr orbital the m is 0 so the two electrons combined have ML = 0. Therefore, the ground state for the H2 molecule is 2E. As in the case of atoms, all filled shells have E S = 0, which results in a JE state. 

As with benzene we study only the tt system using the SEP to account for the presence of the a orbitals. It is not the purpose of this book to compare MCVB with molecular orbital configuration interaction (MOCI) results, but we do it in this case. 

Improvement of the MO method involves better orbitals, better account of interelectronic repulsion, and introduction of mixing of different electron configurations in the molecular orbitals ( configuration interaction ). Improved MO calculations give much more accurate energies at the minimum of a plot such as Figure 21-11, but the bonds still do not dissociate properly, for the same reason as with the simple MO method. 

IV, and the dominant molecular-orbital configurations are given in Table... 

Mapping Molecular Orbital—Configuration Interaction to Valence Bond Wave Functions... 

MAPPING A MOLECULAR ORBITAL CONFIGURATION INTERACTION WAVE FUNCTION INTO A VALENCE BOND WAVE FUNCTION... 

Projecting the Molecular Orbital Configuration Interaction Wave Function Onto the Rumer Basis of Valence Bond Structures... 

Within the independent electron and single active electron approximations, the symmetries of the contributing photoelectron partial waves will be determined by the symmetry of the orbital(s) from which ionization occurs, and so the PAD will directly reflect the evolution of the molecular orbital configuration. Example calculations demonstrating this are shown in Fig. 3 for a model Civ molecule, where a clear difference in the PAD is observed according to whether ionization occurs from an a or an ai symmetry orbital [55] (discussed in more detail below). 

TABLE 7.4 MOLECULAR ORBITAL CONFIGURATIONS AND OTHER DATA ABOUT PERIOD 2 ELEMENTS. IT IS UNDERSTOOD THAT EACH MOLECULE HAS A COMPLETE S1s AND s is ORBITAL. NOTE THAT OXYGEN, FLUORINE, AND NEON HAVE A SLIGHTLY DIFFERENT ORDER DUE TO INTERACTIONS BETWEEN 2s AND 2p ORBITALS. 

The ground state of OH is 2n, arising from the molecular orbital configuration... 

It should be remembered that tbese constants are for the v" = 1 level. A Hartree-Fock wave ftmction for Nj has been calculated by Cade, Sales and Wahl [101], from which the spin rotation and magnetic hyperfine constants were calculated by Rosner, Gaily and Holt [102] they were in excellent agreement with experiment. The dominant molecular orbital configuration, given at the beginning of this section, is... 

A w excited state is assumed to lie 7000 cm" below the w state, which presumably arises from the same molecular orbital configuration. The effect of the estimated level is to increase the entropy by about 0.2 and 1.8 cal K" mol" at 3000 and 6000 K. Bond distances are estimated by comparison with those in Si , C and C . 

Electronic levels (T ) and vibrational-rotational constants are from Rosen (1 ) as supplemented (4) by extensive new data (2, 3, 5, 8, 9). Additional states near 32000 cm" (lOf 3 ) are omitted since their effect is negligible. We estimate unknown spectroscopic constants from known values for states arising from like molecular-orbital configurations (11). Although a is the... 

Theoretical descriptions of low-energy states of biradicals display the presence of two unsaturated valences (biradicals contain one fewer bond than permitted by the rules of valence) the dominant valence bond structures have two dots the low-energy molecular orbital configurations have only two electrons in two approximately nonbonding molecular orbitals two of the natural orbitals have occupancies close to one etc. 

Table 6.4. Molecular orbital configurations and other data about Period 2 elements. It is...

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