dimensional geometry of the molecules is determined by the relative orientation of covalent bonds. In 1957 the Canadian chemist Ron Gillespie based on previous work by Nyholm developed a simple and robust tool to predict the geometry (shape) of the moléculas.La theory he developed is called Repulsion Theory of Electron Pairs Valencia ( TRPEV) and is based on simple argument that groups of electrons will repel each other and form that the molecule is one in which the repulsion between electron groups is TRPEV mínima.Para the groups of electrons can be: a simple link
double a triple bond
link
a nonbonding electron pair
To predict the geometry of a molecule we need to know only how many groups of electrons are related to the central atom for which we write the Lewis formula of the molecule. Then we simply ask how groups of electrons are spatially distributed so that the repulsion between them is minimal.
is important to remember the geometry of the molecule will be determined solely by the spatial distribution of the bonds present and not the position of the nonbonding electron pairs, which if shall be taken into account when determining the spatial arrangement of all e-groups , are such links or no.Por H2S molecule has the formula of Lewis
Here we can identify 4 groups of electrons: two single bonds and two nonbonding electron pairs.
To minimize the repulsions between them adopt a tetrahedral geometry, placing each group at the apex of a tetrahedron whose center is the atom sulfur. But when it comes to determining the geometry of the molecule, it is only determined by the distribution of links, so that the geometry of H2S will be angular.
MSM Note that the angle is less than 109.5 °, the angle of a regular tetrahedron. This is due to the greater repulsion generated by the increasing volume of non-bonding electron pairs.
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