Hybridization sp orbitals and

Carbon and silicon are both iy -hybridized. The C—Si bond involves overlap of a half-filled sp orbital of carbon with a half-filled sp hybrid orbital of silicon. The C—H and Si—H bonds involve hydrogen li orbitals and sp hybrid orbitals of C and Si, respectively. The principal quantum number of the valence orbitals of silicon is 3. 

Figure 1.5 (a) Diagram of atomic orbitals and sp -hybridization, (b) hybrid orbitals of carbon. 

The term sp hybridization indicates that the hybrid orbitals are derived from one s and three p orbitals. Each orbital is said to have 25% s character and 75% p character. The term sp hybridization indicates that the hybrid orbitals are derived from one s and one p orbital. Each orbital is said to have 50% s character and 50% p character. Consequendy, sp hybrid orbitals look more like s orbitals and sp hybridized orbitals look more like p orbitals. 

An alkyl radical is neutral and has one more electron than the corresponding carbocation Thus bonding m methyl radical may be approximated by simply adding an electron to the vacant 2p orbital of sp hybridized carbon m methyl cation (Figure 4 19a) Alternatively we could assume that carbon is sp hybridized and place the unpaired elec tron m an sp orbital (Figure 4 9b)... 

All of these trends can be accommodated by the orbital hybridization model The bond angles are characteristic for the sp sp and sp hybridization states of carbon and don t require additional comment The bond distances bond strengths and acidities are related to the s character m the orbitals used for bonding s Character is a simple concept being nothing more than the percentage of the hybrid orbital contributed by an s orbital Thus an sp orbital has one quarter s character and three quarters p an sp orbital has one third s and two thirds p and an sp orbital one half s and one half p We then use this information to analyze how various qualities of the hybrid orbital reflect those of its s and p contributors... 

Here, the bonding between carbon atoms is briefly reviewed fuller accounts can be found in many standard chemistry textbooks, e.g., [1]. The carbon atom [ground state electronic configuration (ls )(2s 2px2py)] can form sp sp and sp hybrid bonds as a result of promotion and hybridisation. There are four equivalent 2sp hybrid orbitals that are tetrahedrally oriented about the carbon atom and can form four equivalent tetrahedral a bonds by overlap with orbitals of other atoms. An example is the molecule ethane, CjH, where a Csp -Csp (or C-C) a bond is formed between two C atoms by overlap of sp orbitals, and three Csp -Hls a bonds are formed on each C atom. Fig. 1, Al. 

C. The structure, which involves two bridging carbonyl groups as shown in Fig. 26.8a, can perhaps be most easily rationalized on the basis of a bent Co-Co bond arising from overlap of angled metal orbitals (d sp hybrids). However, in solution this structure is in equilibrium with a second form (Fig. 26.8b) which has no bridging carbonyls and is held together solely by a Co-Co bond. 

Hybrid orbital (Section 1.6) An orbital derived from a combination of atomic orbitals. Hybrid orbitals, such as the sp3, s/J2, and sp hybrids of carbon, are strongly directed and form stronger bonds than atomic orbitals do. 

Two other, closely related, consequences flow from our central proposition. If the d orbitals are little mixed into the bonding orbitals, then, by the same token, the bond orbitals are little mixed into the d. The d electrons are to be seen as being housed in an essentially discrete - we say uncoupled - subset of d orbitals. We shall see in Chapter 4 how this correlates directly with the weakness of the spectral d-d bands. It also follows that, regardless of coordination number or geometry, the separation of the d electrons implies that the configuration is a significant property of Werner-type complexes. Contrast this emphasis on the d" configuration in transition-metal chemistry to the usual position adopted in, say, carbon chemistry where sp, sp and sp hybrids form more useful bases. Put another way, while the 2s... 

Fig. 4a, b General models for (a) Jt-type and (b) o-type diradicals, in which the radical orbitals are mainly of the p-character and sp hybrid, respectively... 

Still another aspect of the Li and F valence orbitals is modified by ionic-bond formation. In an isolated ionic or neutral species, each NAO retains the characteristic angular shape of the pure s and p hydrogenic orbitals shown in Fig. 1.1, reflecting the full rotational symmetry of atoms. However, in the presence of another atom or ion this symmetry is broken, and the optimal valence orbitals acquire sp hybrid form (assumed for simplicity to include only valence s and p orbitals), as represented mathematically by... 

Clays contain aluminum oxides in addition to silicon as Si02 and its polymeric forms. Again, there are the p orbitals of oxygen and sp-hybridized orbitals from aluminum, which may result in end-on-end or side-by-side bonding with the same restrictions encountered with silicon. 

This can be thought about either in terms of hybrid orbitals , e.g., pd and sp hybrids as shown above, or alternatively in terms of a Taylor series expansion of a function (d functions are the first derivatives of p functions, p functions are the first derivatives of s functions). While the first way of thinking is quite familiar to chemists (Pauling hybrids), the second offers the advantage of knowing what steps might be taken next to effect further improvement, i.e., adding second, third,.. . derivatives. 

The trick is to make two equivalent orbitals in Be out of the atomic orbitals so that each hydrogen will see essentially the same electronic environment. We can accomplish this by mixing the 2s orbital and one of the empty 2p orbitals (say, the 2p ) to form two equivalent orbitals we call sp" hybrids, since they have both s and p characteristics. As with molecular orbital theory, we have to end up with the same number of orbitals we started with. The bonding lobes on the new spa and spb orbitals on Be are 180° apart, just as we need to form BeH2. In this manner, we can mix any type of orbitals we wish to come up with specific bond angles and numbers of equivalent orbitals. The most common combinations are sp, sp, and sp hybrids. In sp hybrids, one and one p orbital are mixed to get two sp orbitals, both of which... 

In order to minimize the angle strain the C s assume more p character in the orbitals forming the ring and more s character in the external bonds, in this case the C—H bonds. Additional p character narrows the expected angle, while more s character expands the angle. The observed H—C—H bond angle of 114° confirms this suggestion. Clearly, there are deviations from pure p, sp. sp, and sp hybridizations. 

Answer. The orbitals of a normal C—C bond and of the central C—C bond of [ 1.1.1 Jpropellane are shown in Figures B4.1 a and B4.1/), respectively. For both systems, the interacting orbitals are sp" hybrids at about the same energy. The direction of polarization is dictated by the rest of the a framework. In the case of the pro-pellane, the hybrid orbitals are pointed away from each other and therefore interact much more weakly, resulting in a much lower a as LUMO. This accounts for the ease of capture of an electron. The anion would have an electron in this orbital, thereby reducing the bond order and weakening the bond further. 

The increase in acidity by 25 orders of magnitude between sp3- and sp-hybridized carbon acids is similar to that found for the difference in acidity between an ammonium ion (sp3 hybridization) and a protonated nitrile (sp hybridization). It is clear that the hybridization of the orbital they occupy can play a major role in stabilizing electron pairs and thus influencing the effective electronegativity of an atom. 

FIGURE 2.1 Construction of organic hydrocarbons and inorganic carbon families, using the sp, sp2, and sp hybrid orbitals. 

The triple bond is relatively short because of the attractive overlap of three bonding pairs of electrons and the high s character of the sp hybrid orbitals. The sp hybrid orbitals are about one-half s character (as opposed to one-third s character of sp2 hybrids and one-fourth of sp3 hybrids), using more of the closer, tightly held s orbital. The sp hybrid orbitals also account for the slightly shorter C — H bonds in acetylene compared with ethylene. 

New parameters of cyclopropene (155) have been calculated from existing MW data. A near-equilibrium structure has also been derived from scaled moments of iner-tia (Table 16). The lengths of the C—C single bond and the methylene C—H bond and H—C—H angle are similar to those in 1 (Table 1). The C=C bond is, however, considerably shorter than in ethene 1.337 (2) A, and (=)C—H is between C—H in ethene (Section II. A) and in acetylene, 1.0586 and 1.0547 A. Bond-length relations indicate that the methylene carbon in 155 uses approximately the same hybrid orbitals as 1, sp" and sp (Section II.A), to form bonds within the ring and to substituents, while the —CH= carbon in 155 is characterized by sp and sp hybrids, respectively ... 

M—has also been reported for olefins and acetylenes ir-bonded to rhodium and to platinum (6, 21, 46, 87). In the case of rhodium, iy(i°3Rh—is between 10 and 16 Hz for a 7r-bonded olefin (see Table XXVII), while for the cr-bonded carbon in [(C5H5)Rh(ff-C3Hs)-(w-CsHb)], 7( ° Rh—is 26 Hz. It was suggested the bonding of the olefin results from a 60% contribution from a dsp -vnet X orbital and sp -carbon orbital 21). For the olefins and acetylenes w-bonded to platinum 7( Pt—is between 18 and 195 Hz (see Table XXIX) compared to the range of 360 to 1000 Hz reported for carbon cr-bonded to platinum. It was found that 7( Pt— C) is less for a 7r-bonded acetylene than for a rr-bonded ethylene. This was considered as evidence for the Chatt-Dewar-Duncanson molecular orbital model 39, 63) of TT-bonding (XIV), rather than the formally equivalent valence-bond treatment, (XV) and (XVI) 46). However, no allowance appears to have been made for the effect on the hybridization at the carbon of the pseudo-... 

Let us look first for transition-metal compounds that arc truly covalent in the sense of tetrahedral structures and two-electron bonds, which we di.scu.sscd earlier. There are only a few examples. NbN and TaN both form in the wurtzite structure. We presume that bond orbitals of sp hybrids must be present to stabilize the structure this requires three electrons from each transition-metal ion. Both ions are found in column D5 of the Solid State Table, so we anticipate that the remaining two electrons would form a multiplet (as in the ground stale of Ti " ). Thus the effects of the d state are simply added onto an otherwise simple covalent system, just as they were added to a simple ionic system in the monoxides. MnS, MnSe, and MnTe also form a wurtzite structure and presumably may be understood in just the same way. This class of compounds is apparently too small to have been studied extensively. 

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