Linear arrangement hybrid orbitals

The limiting case of it interaction in X—O—X systems occurs when the cr bonds are formed by two linear sp hybrid orbitals on oxygen, thus leaving two pairs of n electrons in pure p orbitals these can then interact with empty dn orbitals on the X atoms so as to stabilize the linear arrangement. Many examples of this are known, e.g., [Cl5Ru—O—RuC15]4 and [(OAc)(py)(Cl)2Os—O—Os(Cl)3(py)2].4... 

A linear arrangement of electron pairs requires two hybrid orbitals, and so we mix an s-orbital with a /7-orbital to obtain two s/7-hybrid orbitals ... 

B Three cr bonds formed from two C2sp hybrids, one bond between the two C atoms and two connecting each C atom to an H atom in a linear arrangement two tt bonds, one between the two C2pv-orbitals and the other between the two C2pv-orbitals. 

Two equivalent ip-hybridized orbitals achieve maximum distance from one another when they arrange in a linear structure ... 

Note that in this case the unshared pairs of electrons are in equatorial positions, which results in a linear structure for IF2 even though the hybrid orbital type is sp3d. It is the arrangement of atoms, not electrons, that determines the structure for a molecule or ion. It is apparent that the simple procedures described in this section are adequate for determining the structures of many molecules and ions in which there are only single bonds and unshared pairs of electrons. 

NO 2, 0=N=0 . N has two cr bonds, no unshared pairs of electrons and therefore needs two hybrid orbitals. N uses sp hybrid orbitals and the cr bonds are linear. The geometry is controlled by the arrangement of the sigma bonds. 

We use different hybridization schemes to describe different arrangements of electron pairs. For example, to explain a trigonal planar electron arrangement, we mix one s-orbital with two p-orbitals and so produce three sp2 hybrid orbitals. They point toward the corners of an equilateral triangle (Fig. 3.19a). A linear arrangement of pairs requires two hybrid orbitals, so we mix an s-orbital with a p-orbital to obtain two sp hybrid orbitals (Fig. 3.19b). Table 3.2 summarizes the relationship between electron arrangement and hybridization type. No matter how many atomic orbitals we mix together, the number of hybrid orbitals is always the same as the number of atomic orbitals we started with, so N atomic orbitals produce N hybrid orbitals. 

Note that the lone pairs are placed in the plane where they are 120 degrees apart. Accommodating five pairs at the vertices of a trigonal bipyramid can be explained if the xenon atom adopts a set of five dsp3 orbitals. Each fluorine atom has four electron pairs and can be assumed to be sp3 hybridized. The XeF2 molecule has a linear arrangement of atoms. 

A linear complex requires two hybrid orbitals 180 degrees from each other. This arrangement is given by an sp hybrid set (Fig. 20.20). Thus in the linear Ag(NH3)2+ ion the Ag1" is described as sp hybridized. 

Most sets of hybrid orbitals are equivalent and symmetric, that is, four sp orbitals directed to the comers of a regular tetrahedron, six tPsp orbitals to the corners of an octahedron, etc. (n the case of hybrids the resulting orbitals are not equivalent. In the trigonal bipyramidal arrangement three orbitals directed trigonally form one set of equivalent orbitals (these may be considered sp hybrids) and two orbitals directed linearly (and perpendicular to the plane of the first three) form a second set of two (these may be considered dp hybrids). The former set is known as the equatorial orbitals and the latter as the axial orbitals. Because of the nature of the different orbitals involved, bonds formed from the two are intrinsically different and will have different properties even when bonded to irJenlica] atoms. For example, in molecules like PFj bond lengths differ for axial and equatorial bonds (see Chapter 6). 

The triple bond in acetylene, like that in nitrogen, is composed of one a and two tt bonds and here also the tt bonds arc formed between electrons in non-hybridized p states. The a electrons, two to each carbon atom, are located in sp hybrid orbitals, formed by the linear combination of one s and one p wave function, as in beryllium, and the molecule is therefore linear. The arrangement of bonds is shown diagrammatically in Figure si. In a similar way the triple bond in the nitrile group G N is composed also of one n and two tt bonds. 

The central carbon forms two xp-hybrids and two unhybridized /7-orbitals, just like acetylene. The j/7-hybrids bond to the terminal carbons in a linear arrangement of cr-bonds. Each p orbital then bonds to a terminal carbon to form a r-bond, as shown below... 

There are no lone pairs on the Hg atom, so the arrangement of the two electron pairs is linear (see Table 10.1). From Table 10.4 we conclude that Hg is ip-hybridized because it has the geometry of the two sp hybrid orbitals. The hybridization process can be imagined to take place as follows. First we draw the orbital diagram for the ground state of Hg ... 

For the trigonal bipyramidal shape of the PCI5 molecule, for example, the VB model proposes that the one 35, the three 3p, and one of the five 3d orbitals of the central P atom mix and form five sp d hybrid orbitals, which point to the vertices of a trigonal bipyramid (Figure 11.6). Seesaw, T-shaped, and linear molecules have this electron-group arrangement with lone pairs in one, two, or three of the central atom s sp d orbitals, respectively. 

Because the triple bond counts as one effective repulsive unit, each carbon has two effective pairs, which requires a linear arrangement. Thus each carbon atom requires5/7 hybridization, leaving two unchanged p orbitals (see Fig. 9.16). One of the oppositely oriented (see Fig. 9.14) sp orbitals is used to form a bond to the hydrogen atom the other sp orbital overlaps with the similar sp orbital on the other carbon to form the sigma bond. The two pi bonds are formed from the overlap of the twop orbitals on each carbon. This accounts for the triple bond (one sigma and two pi bonds) in acetylene. 

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