Sp3 hybrid orbitals of water

More probable representation of the water molecule. The bonding arises from overlap of oxygen sp3 hybrid orbitals with hydrogen Is orbitals. The lone pair on the oxygen is line shaded. The orbitals are displaced tetra-hedrally.. 

Even in the case of s-p orbitals it is not necessary that all the orbitals be equivalent. Consider the water molecule, in which the H—O—H angle is 104 ", which docs not correspond to any of the hybrids described above, but lies between the I09 ° angle for sp3 and 90° for pure p orbitals. Presumably the two bonding orbitals in water are approximately tetrahedral orbitals but contain a little more p character, which correlates with the tendency of the bond angle to diminish toward the 90° of pure p orbitals. The driving forces for this effect will be discussed in Chapter 6. 

To improve our model still further, we have to visualize s- and p-orbitals as waves of electron density centered on the nucleus of an atom. Like waves in water, the four orbitals interfere with one another and produce new patterns where they intersect. These new patterns are called hybrid orbitals. The four hybrid orbitals are identical to one another except that they point toward different comers of a tetrahedron (Fig. 3.16). Each orbital has a node close to the nucleus and a small tail on the other side where the s- and p-orbitals do not completely cancel. These four hybrid orbitals are called sp3 hybrids because they are formed from one s-orbital and three p-orbitals. In an orbital-energy diagram, we represent the hybridization as the formation of four orbitals of equal energy intermediate between the energies of the s- and /7-orbitals from which they are constructed (43). The hybrids are colored green to remind us that they are a blend of (blue) s-orbitals and (yellow) p-orbitals. 

Let us consider the simplest possible case of a system which consists of two orbitals, XA( 1) and / (I), with energies eA and which can interact. It should be emphasized here that these may be orbitals of any kind, atomic orbitals, group orbitals, or complicated MOs. We wish to investigate the results of the interaction between them, that is, what new wave functions are created and what their energies are. Let us also be clear about what the subscripts A and represent. The subscripts denote orbitals belonging to two physically distinct systems the systems, and therefore the orbitals, are in separate positions in space. The two systems may in fact be identical, for example two water molecules or two sp3 hybrid orbitals on the same atom or on different but identical atoms (say, both C atoms). In this case, eA = - Or the two systems may be different in 

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