Theories of Covalent Bonding

Central Themes of VB Theory Types of Hybrid Orbitals 

2 The Mode of Orbital Overlap and the Types of Covalent Bonds Single and Multiple Bonds Mode of Overlap and Molecular Properties 

3 Molecular Orbital (MO) Theory and Electron Delocalization Central Themes of MO Theory Homonuclear Diatomic Molecules of the Period 2 Elements 

Concepts Skills to Review Before You Study This Chapter 

Lewis structures (Section 10.1) resonance in covalent bonding (Section 10.1) 

Like AOs, MOs become txjcupied one electron at a time and have spedfic energy levels. MO theory proposes that the magnetic properties of molecules depend on the number of unpaired elecirons. and the spectral properties arise from elecirons moving to dflerent energy levels as a molecule absorbs or emits energy. 

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We 11 begin our discussion of hydrocarbons by introducing two additional theories of covalent bonding the valence bond model and the molecular orbital model... 

Still another model to represent the bonding that takes place in covalent compounds is the molecular orbital theory. In the molecular orbital (MO) theory of covalent bonding, atomic orbitals (AOs) on the individual atoms combine to form orbitals that encompass the... 

In the molecular orbital (MO) theory of covalent bonding, atomic orbitals form molecular orbitals that encompass the entire molecule. 

Molecular Orbital Theory Model. Oxygen and hydrogen atoms in H2O are held together by a covalent bond. According to the quantum molecular orbital theory of covalent bonding between atoms, electrons in molecules occupy molecular orbitals that are described, using quantum mechanical language, by a linear combination of... 

Obviously, any study of the chemistry of aromatic compounds must begin with a study of benzene. Benzene is unique in that the bonds between the carbon atoms in benzene do not seem to follow the theory of covalent bonds we have developed so far. 

Explain the primary difference between the Heitler-London and Hund-Mulliken theories of covalent bonding. 

We conclude here that the matrix elements of d/dx are constant. This conclusion will follow also from the pseudopotential theory of covalent bonding in Chapter 18, and was found to Idc true of the matrix elements in the nonlocal pscudopotential calculations of Chclikowsky and Cohen (quoted by Phillips,... 

The Nephelauxetic Effect (Section 5) provides evidence for the donation of electron density from ligand to central atom/ion (as suggested by the usual theories of covalent bonding in complexes) and for the delocalization of electrons which, in the CF approach, should be localized in central atom d orbitals. 

After the discovery of the theory of quantum mechanics in 1925 a detailed quantitative theory of covalent bonds was developed. In recent years great progress has been made in understanding valence and chemical combination through the experimental determination of the structures of molecules and crystals and through theoretical studies. The theory of resonance was developed around 193f). 

We know a great deal about the molecular structures of many thousands of compounds, all based on reliable experiments. In our discussion of theories of covalent bonding, we must keep in mind that the theories represent an attempt to explain and organize experimental observations. Eor bonding theories to be valid, they must be consistent with the large body of experimental observations about molec-... 

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