Sp-: hybridized orbitals of methane

Explaining the formation of sp, sp and sp hybrid orbitals in methane, ethene and ethyne 

Figure 1.5 Directional characteristics of sp hybrid orbitals of carbon and the formation of C—H bonds in methane (CH4). The hybrid orbitals point toward the corners of a regular tetrahedron. Hydrogen 1 s orbitals are illustrated in position to form bonds by overlap with the major lobes of the hybrid orbitals.

Fig. 4.4 The sp hybridized orbital on single carbon atoms terminated by four hydrogen atoms forms molecule of methane - CH,

It will thus be apparent why the use of hybrid orbitals, e.g. sp hybrid orbitals in the combination of one carbon and four hydrogen atoms to form methane, results in the formation of stronger bonds. 

Fig. 4. Molecular orbitals showing the hybridization of s and p orbitals, (a) Acetylene (C2H2, sp hybridization) (b) ethylene (C2H4, sp hybridization), and (c) methane (CH4, sp hybridization).

Bonding in methane is most often described by an orbital hybridization model, which is a modified form of valence bond theory. Four equivalent sp hybrid orbitals of carbon are generated by mixing the 2s, 2p, 2py, and 2/) orbitals. In-phase overlap of each half-filled sp hybrid orbital with a half-filled hydrogen lx orbital gives a ct bond. 

The C—H bonds in methane, CH4, are described by valence bond theory as the overlapping of each sp hybrid orbital of the carbon atom with Is orbitals of hydrogen atoms (see Figure 10.22Q. Thus, the bonds are arranged tetrahedrally, which is 

FIGURE 3.14 Each C H bond in methane is formed by the pairing of an electron in a hydrogen U-orbital and an electron in one of the four sp hybrid orbitals of carbon. Therefore, valence-bond theory predicts four equivalent cr-bonds in a tetrahedral arrangement, which is consistent with experimental results. 

The single 2s orbital combines with the three 2p orbitals to create four identical sp hybrid orbitals. The fact that each sp orbital is identical is important because VSEPR theory can now explain the symmetrical shape of methane the tetrahedron. 

A sigma (a) bond is formed between atoms by the overlap of two atomic orbitals along the line that connects the atoms. Carbon uses sp hybridized orbitals to form four such bonds. These bonds are directed from the carbon nucleus toward the corners of a tetrahedron. In methane, for example, the carbon is at the center and the four hydrogens are at the corners of a regular tetrahedron with H-C-H bond angles of 109.5°. 

Qualitative application of VB theory to molecules containing second-row elements such as carbon, nitrogen, and oxygen involves the concept of hybridization, which was deveioped by Linus Pauling. The atomic orbitals of the second-row elements include the spherically symmetric 2s and the three 2p orbitals, which are oriented perpendicularly to one another. The sum of these atomic orbitals is equivalent to four sp orbitals directed toward the corners of a tetrahedron. These are called sp hybrid orbitals. In methane, for example, these orbitals overlap with hydrogen Is orbitals to form CT bonds. 

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