Oxygen atom orbital energies

Orbital correlation diagram for carbon monoxide. The carbon atomic orbital energies are on the left, and the oxygen atomic orbital energies are on the right. The molecular orbitals that form from mixing of the atomic orbitals are represented by the horizontal lines in the center at their approximate orbital energies in the CO molecule. The vertical lines indicate the orbital occupancy. 

A. Radial Functions and Atomic Orbital Energies.—Self-consistent field (SCF) radial functions for vanadium 3d and 4s orbitals were taken from Watson s report.16 Watson gives no 4p function, so it is estimated as having approximately the same radial dependence as the 4s function. Analytic 2s and 2p oxygen SCF radial functions were obtained by fitting the numerical functions given by Hartree17 with a linear combination of Slater functions. These radial functions are summarized... 

Atomic orbital energy level diagrams. To simplify these diagrams, the orbitals are shown at the same energies for different atoms. Actually, the energy of an orbital decreases as the number of protons in the atom increases.Thus the Ip orbitals of fluorine are lower in energy than the Ip orbitals of oxygen. 

There is, in principle, no reason why linear combinations should not be made between AOs which have the correct symmetry but very different energies, such as the lx orbital on the oxygen atom and the lx orbital on the phosphorus atom. The result would be that the resonance integral /i (see Figure 7.12) would be extremely small so that the MOs would be virtually unchanged from the AOs and the linear combination would be ineffective. 

In this case, the ti-MOs resemble those of butadiene. Relative to the butadiene orbitals, however, the acrolein orbitals lie somewhat lower in energy because of the effect of the more electronegative oxygen atom. This factor also increases the electron density at oxygen relative to carbon. 

The goodness of the PP representation can be checked by comparing the all-electron and PP orbital energies and relative stability of atomic states. The comparison is shown in Table 4, and is seen to be very satisfying. For a balanced treatment, also the carbon and oxygen atoms were treated by a PP, as described in previous work5.3d functions were not introduced in the sulphur basis set, mainly because they were not deemed necessary for the illustrative purposes of this chapter. Also, the derivation of a PP representation for polarization functions is not a straightforward matter. The next section is devoted to the discussion of this point. 

Figure 2.14. The molecular orbitals of gas phase carbon monoxide, (a) Energy diagram indicating how the molecular orbitals arise from the combination of atomic orbitals of carbon (C) and oxygen (O). Conventional arrows are used to indicate the spin orientations of electrons in the occupied orbitals. Asterisks denote antibonding molecular orbitals, (b) Spatial distributions of key orbitals involved in the chemisorption of carbon monoxide. Barring indicates empty orbitals.5 (c) Electronic configurations of CO and NO in vacuum as compared to the density of states of a Pt(lll) cluster.11 Reprinted from ref. 11 with permission from Elsevier Science.

Such an orbital phase picture in Fig. 14 is also applicable to rationalize the relative S-T gaps of hetero diradicals 19 and 20. hi comparison with their parent system, 1,3-dimethylenecyclobutadiene (DMCBD, 10), the introduction of oxygen atoms does destabilize the triplet state. The calculated energy gap between singlet and triplet states, AE deaeases in the order 10 (18.2 kcal moF ) > 19 (7.7 kcal moF ) > 20 (-20.7 kcal moF ) [64]. These results supported the orbital phase predictions. 

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