Hybrid orbital sp3d hybridization

XeF2 There are 10 valence electrons (8 from valence shell of xenon 5s2 5p6 and two form the two bonded fluorine atoms) to be filled in orbitals. These require five orbitals which can be formed by the hybridisation of one 5s, three 5p and one 5d orbitals (sp3d hybridization). These are directed towards the five comers of a trigonal bipyramid. Two of these contain shared electrons, the other three lone pairs. For greatest stability, the shared pairs are as far apart as possible, so Xe - F bonds are at 180° to each other and the stmcture is linear. 

Figure 2. Diagrams showing the directions of the maxima of octahedral sp3d2 and trigonal bipyramidal and square pyramidal sp3d hybrid orbitals.

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. 

Next we must select a hybridization scheme for the Br atom that is compatible with the predicted shape. It turns out that only sp3d hybridization will provide the necessary trigonal bipyramidal distribution of electron pairs around the bromine atom. In this scheme, one of the sp3d hybrid orbitals is filled while the remaining four are half-occupied. 

The four Br—F bonds in the cation are then formed by the overlap of the half-filled sp3d hybrid orbitals of the bromine atom with the half-filled p-orbitals of the terminal fluorine atoms. Thus, by using sp3d hybridization, we end up with the same see-saw molecular geometry for the cation as that predicted by VSEPR theory (when the lone pair on Br is ignored). 

Hybrid orbitals formed two sp three sp2 foursp3 one d five sp3d two d six sp3d2... 

In an sp3d hybridized phosphorus atom in a TBP molecule, will the atom have a greater electronegativity when bonding through equatorial or axial orbitals Explain. 

FIGURE 3.20 One of the five sp3d hybrid orbitals, and their five directions, that may be formed when d-orbitals are available and we need to reproduce a trigonal bipyramidal arrangement of electron pairs. 

SOLUTION According to Example 3.3, SF4 has a trigonal bipyramidal arrangement of electron pairs. We can construct five equivalent hybrid orbitals by mixing an s-orbital with three p-orbitals and one d-orbital. The result is five sp3d orbitals. 

FIGURE 7.12 The five sp3d hybrid orbitals and their trigonal bipyramidal geometry. 

Hybridization of five atomic orbitals occurs by a combination of one s orbital, three p orbitals, and one d orbital, giving five sp3d hybrid orbitals in a trigonal bipyramidal arrangement (Figure 7.12). Three of the hybrid orbitals lie in a plane at angles of 120°, with the remaining two orbitals perpendicular to the plane, one above and one below. 

Unlike carbon, the valence shell of the silicon atom has available d orbitals. In many silicon compounds, the d orbitals of Si contribute to the hybrid orbitals and Si forms more than four 2c-2e covalent bonds. For example, Sib s- uses sp3d hybrid orbitals to form five Si-F bonds, and SiF62 uses sp3d2 hydrid orbitals to form six Si-F bonds. 

The compound F4P-NEt2 has this bonding type, in which the P atom uses sp3d hybrid orbitals. 

This type of hybridization is known as sp3d (or dsp3, depending on where you look). The remaining type of hybridization, known as sp3cf (cfsp3), can be seen in the hybridization of sulfur in the compound sulfur hexafluoride, SF6. In Figure 7.21 below, note how two electrons are promoted to the d orbitals ... 

In a molecule in which the central atom exhibits sp3d hybrid orbitals, the electron pair arrangements form the shape of a(n)... 

This structure is somewhat unusual in that the two bonds in axial positions are longer than those in the equatorial positions. The hybrid bond type for the trigonal bipyramid is sp3d (or dsp3 in some cases). However, in reality this is a combination of dp (linear) and sp2 (trigonal planar) hybrids so the orbitals used in the axial and equatorial positions are not equivalent, and this is apparent from the bond lengths shown on the preceding structure. 

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