Lecture 25: Introduction to Molecular Orbital

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Lecture 25 Introduction to Molecular Orbital
Theory The material in this lecture covers the
following in Atkins. 14
Molecular structure Molecular
Orbital Theory (a) Linear
combinations of atomic orbitals
(b) bonding orbitals (c)
anti-bonding orbitals Lecture
on-line Introduction to Molecular
Orbital theory (PowerPoint)
Introduction to Molecular Orbital Theory (PDF)
Handout for this lecture
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Molecular Orbital Theory
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(b) a contour representation of the amplitude.
(a)The amplitude of the bonding molecular
orbital in a hydrogen molecule-ion in a plane
containing the two nuclei and
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A representation of the constructive
interference that occurs when two H 1s orbitals
overlap and form a bonding ? orbital. Compare
this illustration with Fig.14.14.
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The boundary surface of a ? orbital encloses
the region where the electrons that occupy the
orbital are most likely to be found. Note that
the orbital has cylindrical symmetry.
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The electron density calculated by forming the
square of the wavefunction used to construct
Fig.14.14. Note the accumulation of electron
density in the internuclear region.
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The calculated and experimental molecular
potential energy curves for a hydrogen
molecule-ion.
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A representation of the destructive interference
that occurs when two H1s orbitals overlap and
form an antibonding ? orbital. Compare this
illustration with Fig.14.20.
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(a) The amplitude of the antibonding molecular
orbital in a hydrogen molecule-ion in a plane
containing the two nuclei and
(b) a contour representation of the amplitude.
Note the internuclear node.
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The electron density calculated by forming the
square of the wavefunction used to construct
Fig.14.20. Note the elimination of electron
density from the internuclear region.
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A partial explanation of the origin of bonding
and antibonding effects.
(b) In an antibonding orbital, the nuclei are
attracted to an accumulation of electron
density outside the internuclear region.
(a) In a bonding orbital, the nuclei are
attracted to the accumulation of electron
density in the internuclear region.
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A molecular orbital energy level diagram for
orbitals constructed from the overlap of H1s
orbitals the separation of the levels
corresponds to that found at the equilibrium
bond length. The ground electronic
configuration of H2 is obtained by
accommodating the two electrons in the lowest
available orbital (the bonding orbital).
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