Application examples of hybrid orbital theory

1) sp hybridization

The gaseous BeCl ₂ molecule is linear, and the valence electron configuration of the Be atom is 2s ² 2p ⁰
.

In order to form two covalent bonds, an electron is excited from the 2s orbital into the 2p orbital so that the valence layer of Be has two single electrons

The CO ₂ molecule is linear
.

C atom adopts sp isotropic hybridization [Figure 6-15(b)]

Figure 6-15 Excitation and sp hybridization of beryllium and carbon atoms

In the CO ₂ molecule, the two 2p orbitals of the unhybridized C atom have single electrons, and each form a π bond with the 2p orbital of O, that is, the C atom and two O form two mutually perpendicular π bonds (Figure 6-16)
.

Figure 6-16 The mutually perpendicular π bonds in the CO ₂ molecule

From the molecular configuration and bonding of BeCl ₂ and CO ₂ we know that the molecular configuration is determined by the σ bond
.

2) sp ² hybrid

The molecular configuration of BCl ₃ is triangular, and its bond formation and molecular configuration can be discussed using hybrid orbital theory
.

The valence electron configuration of B is 2S ² 2p ¹ , in order to form 3 covalent bonds, it takes sp2 isotropic hybridization after exciting an electron (Figure 6-17)

6-17 Excitation of boron atom and sp ² hybridization

The bond angle of HCH and HCC in the ethylene (H ₂ C=CH ₂ ) molecule is about 120°
.

With one C as the center and the other C constituting the CH ₂ ligand, the 3 ligands around the center C form a triangular structure, indicating that C adopts sp ² hybridization, as shown in Figure 6-14(b)

3) sp3 hybridization

The CH ₄ and CCl ₄ molecules are in a regular tetrahedral configuration, and the bond angles are both 109°28'
.

The C atom in the molecule adopts sp ³ equivalent hybridization, as shown in Figure 6-14(a)

4) Hybridization of sp ³ d and sp ³ d ²

The gaseous PF ₅ and PCl ₅ molecules have a triangular bipyramid configuration
.

When bonding, one 3s electron of P atom is excited to 3d orbital, and sp ³ d hybridization is adopted [Figure 6-18(a)].
The 5 hybridized orbitals are distributed in triangular double cones, forming σ bonds with halogen atoms respectively, so The molecules of PF ₅ and PCl ₅ have a triangular bipyramid configuration

The SeF ₆ molecule has an octahedral configuration
.

One 4s orbital electron and one 4p orbital electron of Se atom are excited to 4d orbital, and there are 6 single electrons in total

Figure 6-18 sp ³ d and sp ³ d ² isotropic hybrid orbitals

5) unequal hybridization

The NH ₃ molecule has a triangular pyramid shape
.
According to the theory of mutual exclusion of electron pairs in the valence layer, the valence layer of the N atom has 4 pairs of electrons, 3 pairs of electrons are used to form NH bonds, and 1 lone electron pair
.

There are 3 NH bonds and 1 lone electron pair in the NH ₃ molecule, and N adopts sp ³ unequal hybridization, as shown in Figure 6-19(a)
.
The three framework orbitals with single electrons form σ bonds with H respectively, and the hybrid orbitals with lone electron pairs do not form bonds, as shown in Figure 6-19(c)
.

The H ₂ O molecule has a V-shaped structure
.
The H ₂ O molecule has 2 HO bonds and 2 lone electron pairs, and O adopts sp ³ unequal hybridization, as shown in Figure 6-19(b)
.
The two hybrid orbitals with single electrons respectively form a σ bond with H(, while the hybrid orbitals with lone electron pairs do not form a bond, as shown in Figure 6-19(d)
.

Figure 6-19 Hybridization and molecular structure of orbitals in NH and H ₂ O molecules

Since NH _.
3
lone electron pairs NH molecules bonded electron pair repulsion, NH _.
3
bond angle becomes small molecules, is not 109 ° 28 ', but [deg.
] 42 is 106'
.
In the same way, the lone electron pair reduces the bond angle of the H ₂ O molecule to 104°31'
.

Related links: Concepts and types of hybrid orbital theory