Molecular orbital diagrams diatomic molecules

The actual energies of molecular orbitals for diatomic molecules are intermediate between the extremes of this diagram, approximately in the region set off by the vertical lines. Toward the right within this region, closer to the separated atoms, the energy sequence is the normal one of O2 and F2 further to the left, the order of molecular orbitals is that of B2, C2 and N2, with a-g(2p) above TT (2p). 

In this chapter the necessary theory to understand these two approaches is outlined. Orbital symmetry is introduced by consideration of atomic orbitals and their interaction to form molecular orbitals. The construction of correlation diagrams is illustrated for the formation of molecular orbitals of diatomic molecules. 

The data show that bond energies for these three diatomic molecules increase moving across the second row of the periodic table. We must construct molecular orbital diagrams for the three molecules and use the results to interpret the trend. 

Draw a schematic molecular orbital diagram for the adsorption of a diatomic molecule on a d metal. 

FIGURE 3.8 Molecular orbital diagrams for second-row homonudear diatomic molecules. 

In addition to the homonudear molecules, the elements of the second period form numerous important and interesting heteronudear species, both neutral molecules and diatomic ions. The molecular orbital diagrams for several of these species are shown in Figure 3.9. Keep in mind that the energies of the molecular orbitals having the same designations are not equal for these species. The diagrams are only qualitatively correct. 

As can be seen from its ground-state molecular orbital diagram in Figure 4.11, dioxygen has a paramagnetic ground state. It is the only stable homonuclear diatomic molecule with this property. 

Density Functional Theory, DFT (B3LYP), CASSCF (Complete Active-State Self-Consistent Field) and MRSD-CI (Multi-Reference Single-Double Correlation Interaction) calculations on the diatomic units AuO, AuO", AuO " and AuO " clearly show that stability of Au-0 bond reduces in this order. This trend is consistent with the molecular orbital diagram of AuO molecule presented in Fig. 10. 

Construct the molecular orbital diagram for diatomic nitrogen, N2. Is this molecule paramagnetic or diamagnetic ... 

Figure 1.9 Molecular orbital diagram for the general case of a diatomic molecule AB, where B is more electronegative than A. Reprinted, by permission, from R. E. Dickerson, H. B. Gray, and G. P. Haight, Jr., Chemical Principles, 3rd ed., p. 464. Copyright 1979 by Pearson Education, Inc.

Figure 4.2 The molecular orbital diagrams for homonuclear diatomic molecules of the second short period, Li. to Ne2. Diagram (a) is appropriate for 02, F2 and Ne2, diagram (b) for the molecules Li2 to N2...

The molecular orbital diagram for the nitrogen monoxide molecule is shown in Figure 4.6. The orbitals are produced from the same pairs of atomic orbitals as in the cases of the homonuclear diatomic molecules of Section 4.2. 

Figure 2-12 Energy diagrams for a homonuclear diatomic molecule. Note that the differences in the energy levels of the atoms are larger than the energy differences between the molecular orbitals. Diagram (a) is appropriate for no interaction between 2s and 2p levels, and diagram (b) is appropriate for substantial interaction between 2s and 2p levels. Refer to pp. 36-38.

FIGURE 7.20 Molecular orbital diagrams for the second-row diatomic molecules (a) N2, (b) 02, and (c) F2. The 02 molecule has two unpaired electrons in its two degenerate 77 2p orbitals and is therefore paramagnetic. 

The oxygen molecule is diatomic, and the molecular orbital diagram for the molecule is shown in Figure 14.1. 

Homonuclear diatomic ions can be treated in a manner similar to that used for neutral molecules. Although the relative energies of molecular orbitals in such ions may be somewhat different than in the neutral molecules, in general the molecular orbital diagram for the molecules may be used for the ions simply by adjusting the electron count. For example, the molecular orbitals of the ions 02+, 02, and 022- may be described using the orbitals for neutral 02 in Figure 2-4. 

Prepare a molecular orbital energy level diagram for nitric oxide (NO) and predict the bond order of this molecule. On the basis of the molecular orbital diagram, what do you predict for the bond orders of NO+ and NO Which of these diatomic species would you expect to have the shortest bond length Why ... 

Figure 4.8 The molecular orbital diagram of the diatomic molecule...

Your molecular orbital diagram should look like figure 2.18 which shows the MO diagram for Period 2 homonuclear diatomic molecules from Li2 to N2. Each carbon atom has four valence electrons, thus a total of 8 electrons has to be placed in the molecular orbitals on the diagram. Keep in mind that you still follow the Hund s rule and the Pauling exclusion principle when filling molecular orbitals with electrons. See the solution for E2.22... 

The P2 molecule contains phosphorus atoms from the third row of the periodic table. We will assume that the diatomic molecules of the Period 3 elements can be treated In a way very similar to that which we have used so far. Thus we will draw the MO diagram for P2 analogous to that for N2. The only change will be that the molecular orbitals will be formed from 35 and 2p atomic orbitals. The P2 model has 10 valence electrons (5 from each phosphorus atom). The resulting molecular orbital diagram is... 

MOLECULAR ORBITAL DIAGRAM OF CERTAIN HOMONUCLEAR DIATOMIC MOLECULES... 

The O2 molecule has 12 valence electrons (6 + 6) 62 has 11 valence electrons (6 + 6 - 1) and 02 has 13 valence electrons (6 + 6 + 1). We will assume that the ions can be treated using the same molecular orbital diagram as for the neutral diatomic molecule ... 

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