Hybrid orbital Hybridization

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. 

It is important to realize that methane is not tetrahedral because carbon has sp3, hybrid orbitals. Hybridization is only a model—a theoretical way of describing the bonds that are needed for a given molecular structure. Hybridization is an interpretation of molecular shape shape is not a consequence of hybridization. 

Another type of orbital is one that originates from the mixing of the different atomic orbitals and is called a hybrid orbital. Hybridization (mixing) of atomic orbitals results in a new set of orbitals with different... 

Tetrahedral geometry with sp3 hybrid orbitals. Hybridization of an s orbital with all three p orbitals gives four sp3 hybrid orbitals with tetrahedral geometry corresponding to 109.5° bond angles. 

Hybrid Orbitals Hybridization Geometry Approximate Bond Angles... 

Hybridized orbitals Hybridized orbital Hiickel theory41-45) Independent electron molecular orbital theory48) Zero-differential overlap approximation48) Orthogonalized SCF method71) ... 

Hybrid orbitals are named by indicating the number and kind of atomic orbitals hybridized. Hybridization of one s orbital and onep orbital gives two sp hybrid orbitals. We shall see presently that hybridization of one s and two p orbitals gives three sp hybrid orbitals hybridization of one s orbital and three p orbitals gives four sp hybrids, and so on (see Table 8-2). 

Trigonal geometry with sp hybrid orbitals. Hybridization of an orbital with two p orbitals gives a set of three sp hybrid orbitals. The bond angles associated with this trigonal structure are about 120°. The remaining p orbital is perpendicular to the plane of the three hybrid orbitals. 

The s and p orbitals used in the quantum mechanical description of the carbon atom, given in Section 1.10, were based on calculations for hydrogen atoms. These simple s and p orbitals do not, when taken alone, provide a satisfactory model for the tetravalent— tetrahedral carbon of methane (CH4, see Practice Problem 1.22). However, a satisfactory model of methane s structure that is based on quantum mechanics can be obtained through an approach called orbital hybridization. Orbital hybridization, in its simplest terms, is nothing more than a mathematical approach that involves the combining of individual wave functions for r and p orbitals to obtain wave functions for new orbitals. The new orbitals have, in varying proportions, the properties of the original orbitals taken separately. These new orbitals are called hybrid atomic orbitals. 

The promotion of a 2s electron to a 2p orbital in Be requires energy. Why, then, do we envision the formation of hybrid orbitals Hybrid orbitals have one large lobe and can therefore be directed at other atoms better than can unhybridized atomic orbitals. Hence, they can overlap more strongly with the orbitals of other atoms than atomic orbitals, and stronger bonds result. The energy released by the formation of bonds more than offsets the energy that must be expended to promote electrons. 

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