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Unformatted text preview: Diatomic Molecules 14th May 2009 1 Chemical Bonds in Diatomic Molecules: Over- laps and Delocalization of Electrons 1.1 H + 2 Molecule Consider the process where 2 atomic nuclei and associated electron (1 electron atom) are brought closer together from ∞ . What happens to the distribution of electronic density as a result of this process? Essentially, we are asking what happens when we form a chemical bond. • Many-Electron Atoms: Atomic Wavefunction derived from Atomic or- bitals • Many-Atom Molecules: Molecular Wavefunction derived from Molec- ular orbitals • Many-Atom Molecules: Molecular Orbitals derived from Atomic Or- bitals LCAO-MO For this case, the molecular orbital can be drived from atomic orbitals on each nucles. Since there is only one electron, we can start with the simplest molecular orbital as a linear combination of atomic orbitals (LCAO-MO): σ = c a φ H 1 s a ± c b φ H 1 s b If we consider the spatial extent of the molecular orbital, we see that there are 2 cases: 1 The first case corresponds to a bonding orbital and the second to an anti-bonding orbital We can also consider the probability density for the electron being in the volume around the nuclei: • Electrons in a chemical bond are thus...
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