Atomic orbitals orbital mixing

The VSEPR theory is only one way in which the molecular geometry of molecules may be determined. Another way involves the valence bond theory. The valence bond theory describes covalent bonding as the mixing of atomic orbitals to form a new kind of orbital, a hybrid orbital. Hybrid orbitals are atomic orbitals formed as a result of mixing the atomic orbitals of the atoms involved in the covalent bond. The number of hybrid orbitals formed is the same as the number of atomic orbitals mixed, and the type of hybrid orbital formed depends on the types of atomic orbital mixed. Figure 11.7 shows the hybrid orbitals resulting from the mixing of s, p, and d orbitals. 

With a total of fourteen valence electrons to accommodate in molecular orbitals, ethane presents a more complicated picture, and we now meet a C—C bond. We will not go into the full picture—finding the symmetry elements and identifying which atomic orbitals mix to set up the molecular orbitals. It is easy enough to see the various combinations of the Is orbitals on the hydrogen atoms and the 2s, 2px, 2py and 2pz orbitals on the two carbon atoms giving the set of seven bonding molecular orbitals in Fig. 1.19. 

Look again at Table 9-3 on the previous page. Notice that the number of atomic orbitals mixed to form the hybrid orbital equals the total number of pairs of electrons. In addition, the number of hybrid orbitals formed equals the number of atomic orbitals mixed. For example, AICI3 has a total of three pairs of electrons and VSEPR predicts a trigonal planar molecular shape. To have this shape, one s and two p orbitals on the central atom A1 must mix to form three identical sp hybrid orbitals. 

The energies of the set of 3d states and those of the 2p states have also been separated a bit in this correlation diagram to make it easier to see which atomic orbitals mix to form which molecular orbitals. 

Electrons Behave as Waves Standing Waves in One and Two Dimensions Standing Waves in Three Dimensions Atomic Orbitals Mixing Atomic Orbitals into Molecular Orbitals Bonding and Antibonding MOs of Hydrogen... 

Atomic Orbitals Mixed from Valence Shell of Central Atom... 

The induced transition dipole moments by the SAC-Cl method are shown in Fig. 39.8 as a function of the intemuclear distance. These induced moments are mainly due to the intra-atomic orbital mixing of the p-component of the Cs atom, caused by a reduction of the spatial symmetry of the system. The 6s2-5dS transition moment is induced at larger intemuclear distances than that of 6s2-7s2. The magnitude of the transition moment is reversed between the 5dS and 7s2 states at the avoided crossing point. 

The notation sp means that one s atomic orbital and one p atomic orbital mix to form a set of two hybrid orbitals with different directional properties. 

The number of hybrid orbitals obtained equals the number of atomic orbitals mixed. 

You can imagine hybridization as a process in which atomic orbitals mix, hybrid orbitals form, and electrons enter them with spins parallel (Hund s rule) to create stable bonds. In truth, though, hybridization is a mathematically derived result from quantum mechanics that accounts for the molecular shapes we observe. 

VB theory explains that a covalent bond forms when two atomic orbitals overlap and two electrons with paired (opposite) spins occupy the overlapped region. Orbital hybridization allows us to explain how atomic orbitals mix and change their characteristics during bonding. Based on the observed molecular shape (and the related electron-group arrangement), we postulate the type of hybrid orbital needed. 

I n. 5 Give the number and type of hybrid orbital that forms when each set of atomic orbitals mixes ... 

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