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Theories of Covalent Bonding Valence Bond (VB) Theory and Orbital Hybridization The Mode of Orbital Overlap and the Types of Covalent Bonds.

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Presentation on theme: "Theories of Covalent Bonding Valence Bond (VB) Theory and Orbital Hybridization The Mode of Orbital Overlap and the Types of Covalent Bonds."— Presentation transcript:

1 Theories of Covalent Bonding Valence Bond (VB) Theory and Orbital Hybridization The Mode of Orbital Overlap and the Types of Covalent Bonds

2 The Central Themes of VB Theory Basic Principle A covalent bond forms when the orbitals of two atoms overlap and the overlap region, which is between the nuclei, is occupied by a pair of electrons. The two wave functions are in phase so the amplitude increases between the nuclei.

3 The Central Themes of VB Theory Themes A set of overlapping orbitals has a maximum of two electrons that must have opposite spins. The greater the orbital overlap, the stronger (more stable) the bond. The valence atomic orbitals in a molecule are different from those in isolated atoms. There is a hybridization of atomic orbitals to form molecular orbitals.

4 Orbital overlap and spin pairing in three diatomic molecules. Hydrogen, H 2 Hydrogen fluoride, HF Fluorine, F 2

5 Hybrid Orbitals The number of hybrid orbitals obtained equals the number of atomic orbitals mixed. The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed. Key Points spsp 2 sp 3 sp 3 dsp 3 d 2 Types of Hybrid Orbitals

6 The sp hybrid orbitals in gaseous BeCl 2. atomic orbitals hybrid orbitals orbital box diagrams

7 The sp hybrid orbitals in gaseous BeCl 2. orbital box diagrams with orbital contours

8 The sp 2 hybrid orbitals in BF 3.

9 The sp 3 hybrid orbitals in CH 4.

10 The sp 3 hybrid orbitals in NH 3.

11 The sp 3 hybrid orbitals in H 2 O.

12 The sp 3 d hybrid orbitals in PCl 5.

13 The sp 3 d 2 hybrid orbitals in SF 6.

14

15 The  bonds in ethane(C 2 H 6 ). both C are sp 3 hybridized s-sp 3 overlaps to  bonds sp 3 -sp 3 overlap to form a  bond relatively even distribution of electron density over all  bonds

16 The  and  bonds in ethylene (C 2 H 4 ).

17 The  and  bonds in acetylene (C 2 H 2 ).

18 The paramagnetic properties of O 2


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