Hybridization of orbitals

FIGURE 14.1 Electron structures of elemental carbon before hybridization. (a) Electron configuration, (b) orbital diagram, and (c) Lewis structure. 

FIGURE 14.2 Lewis structures showing that all four electrons on a carbon become unpaired during hybridization. 

This produces a capability for covalent bonding that is unique. In all organic compounds—from the very simple to those that possess a complex network structure—carbon atoms always bond four times. While there may be single bonds, double bonds, and triple bonds involved, the total number of bonds to any carbon atom is always four—-no more and no less—because of the four unpaired electrons resulting from hybridization. 

One final point is that there can be p orbitals still remaining after hybridization. That is why double bonds and triple bonds are possible in organic compounds. Recall that the second bond of a double bond is a pi (Jt)-bond (overlap of two p orbitals) and that the second and third bonds of a triple bond are 7t-bonds. 

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Although we have described the structures of several molecules in terms of hybrid orbitals and VSEPR, not all structures are this simple. The structures of H20 (bond angle 104.4°) and NH3 (bond angles 107.1°) were described in terms of sp3 hybridization of orbitals on the central atom and comparatively small deviations from the ideal bond angle of 109° 28 caused by the effects of unshared pairs of electrons. If we consider the structures of H2S and PH3 in those terms, we have a problem. The reason is that the bond angle for H2S is 92.3°, and the bond angles in PH3 are 93.7°. Clearly, there is more than a minor deviation from the expected tetrahedral bond angle of 109° 28 caused by the effect of unshared pairs of electrons ... 

The bond angle in ONC1 is 116 °. Explain what this means in terms of hybridization and how hybridization of orbitals on N allows a 7r bond to be present. 

In his thorough discussion of spd hybrid orbitals Hultgren3 proved several interesting theorems. One of them is that the best bond orbital that can be formed by hybridization of orbitals constituting one or... 

In the valence bond theory, hybridization of orbitals is an integral part of bond formation. As we shall see, the concept need not be explicitly considered in molecular orbital theory but may be helpful in visualizing the process of bond formation. 

The variety in properties of different produced carbon materials is conditioned by the electronic structure of a carbon atom. The redistribution of electron density, the formation of electronic clouds of different modifications around the atoms, the hybridization of orbitals (sp3-, sp2-, sp- hybridization) are responsible for the existence of different crystalline allotropic phases and their modifications. 

Valence bond hybridization of orbitals, resonance, and sigma and pi bonds... 

The answer comes from a process known as hybridization of orbitals. The basic premise is that in order to gain the stability of additional covalent bonds, some electrons can be... 

As you saw in Chapter 6, some atoms can violate the octet rule by using unoccupied dorbitals in the same energy level. This process actually occurs by hybridization—promoting electrons into the unoccupied d orbitals. For example, look at the hybridization of orbitals in the phosphorus atom as it is seen in PC15 in Figure 7.20 ... 

Valence bond theory predicts the hybridization of orbitals, which occurs when an atom promotes an electron from a lower to a higher energy level in order to form more bonding pairs. You should be familiar with the five types of hybridizations (sp, sp2, sp3, dsp3, cfsp3). 

At this point, we can consider some general rules for determining the hybridization of orbitals and the bond angles of atoms in organic molecules. After stating these rules, we solve some problems to show how the rules are used. 

The d orbitals in an atom also take part in hybridization, leading to hybrid orbitals such as dsp" or d sp. There is a definite relationship between the structure of molecules and the hybridization of orbitals. Table 3.1 (p. 62) lists various hybrid orbitals and the resulting structures. "... 

TIte NHj molecule if tiiere were no hybridization of orbitals... 

Draw the Lewis formula of an ammonium ion. Describe the formation of the ammonium ion from ammonia plus H. Does the hybridization of orbitals on nitrogen change during the formation of the ammonium ion Do the bond angles change ... 

Knowledge Required (1) The valence-shell-electron-pair-repulsion (VSEPR) model for predicting molecular shape. (2) The valence-bond theory for predicting hybridization of orbitals. 

The conduction band where unoccupied MO of CeOg polyhedra form is almost diminished (as expected) because Ca atom is located on the same position of Ce site statistically in this calculation. Interestingly, the structure of valence band was little changed and the top of valence band returned to the T point. This results direct transition of photo-assist excitation. The band edge spectra will be expected as a sharpened one by doping Ca. It can be considered that the band gap was extended by tightly bonded to make new hybridization of orbital both Ca 2s and Ce 4f. Because of this, it can be explained electronically that Ce02 loses the semiconductor property to be more stable compound. 

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