Presentation on theme: "Theories of Covalent Bonding"— Presentation transcript:
1 Theories of Covalent Bonding Valence Bond (VB) Theory and Orbital HybridizationThe Mode of Orbital Overlap and the Types of Covalent Bonds
2 The Central Themes of VB Theory Basic PrincipleA 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 increasesbetween the nuclei.
3 The Central Themes of VB Theory 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 molecularorbitals.
4 Orbital overlap and spin pairing in three diatomic molecules. Hydrogen, H2Hydrogen fluoride, HFFluorine, F2
5 Hybrid Orbitals Key Points 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.Types of Hybrid Orbitalsspsp2sp3sp3dsp3d2
6 The sp hybrid orbitals in gaseous BeCl2. atomic orbitalshybrid orbitalsorbital box diagrams
7 The sp hybrid orbitals in gaseous BeCl2. orbital box diagrams with orbital contours
15 relatively even distribution of electron density over all s bonds The s bonds in ethane(C2H6).both C are sp3 hybridizeds-sp3 overlaps to s bondssp3-sp3 overlap to form a s bondrelatively even distribution of electron density over all s bonds