Geometris dan Struktur Elektronik Molekul
geometric and of the electronic structure of molecules
The connection between the two will be provided by the molecular symmetry,
or rather its expression in what is called group theory
If you were to briefly close and
then open your eyes you would have no means of telling whether someone had rotated
the model so that, although each hydrogen atom had been moved, the final position of
the model was indistinguishable from its starting position.
The symmetry of a molecule is characterized by the fact that
it is possible, hypothetically at least, to carry out operations which, whilst interchanging
the positions of some (or all) of the atoms in the molecule, lead to arrangements of atoms
which are indistinguishable from the initial arrangement.
two closely related concepts. Symmetry elements and symmetry operations.
Examples of symmetry elements are rotation axes, mirror planes and centres of symmetry.
Examples of symmetry operations are those of rotation about an axis,
reflection in a mirror plane and inversion in a centre of symmetry
The word ‘group’arises from the fact that the set of operations satisfy all of
the requirements of mathematical group theory.
In determining the effect of symmetry on physical properties, there are four
symmetries to be considered:
(1) the symmetry of the material,
(2) the symmetry of the external forces,
(3) the symmetry of resulting change or displacement,
(4) the symmetry of the physical property relating displacement to external force.
Here we are using the terms force and displacement in the general sense to
include electric, magnetic, and thermal quantities as well as mechanical effects.
The connection between the two will be provided by the molecular symmetry,
or rather its expression in what is called group theory
If you were to briefly close and
then open your eyes you would have no means of telling whether someone had rotated
the model so that, although each hydrogen atom had been moved, the final position of
the model was indistinguishable from its starting position.
The symmetry of a molecule is characterized by the fact that
it is possible, hypothetically at least, to carry out operations which, whilst interchanging
the positions of some (or all) of the atoms in the molecule, lead to arrangements of atoms
which are indistinguishable from the initial arrangement.
two closely related concepts. Symmetry elements and symmetry operations.
Examples of symmetry elements are rotation axes, mirror planes and centres of symmetry.
Examples of symmetry operations are those of rotation about an axis,
reflection in a mirror plane and inversion in a centre of symmetry
The word ‘group’arises from the fact that the set of operations satisfy all of
the requirements of mathematical group theory.
In determining the effect of symmetry on physical properties, there are four
symmetries to be considered:
(1) the symmetry of the material,
(2) the symmetry of the external forces,
(3) the symmetry of resulting change or displacement,
(4) the symmetry of the physical property relating displacement to external force.
Here we are using the terms force and displacement in the general sense to
include electric, magnetic, and thermal quantities as well as mechanical effects.
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