Valence-shell electron-pair repulsion theory VSEPR

Now that we know how to determine hybridization states, we need to know the geometry of each of the three hybridization states. One simple theory explains it all. This theory is called the valence shell electron pair repulsion theory (VSEPR). Stated simply, all orbitals containing electrons in the outermost shell (the valence shell) want to get as far apart from each other as possible. This one simple idea is all you need to predict the geometry around an atom. First, let s apply the theory to the three types of hybridized orbitals. 

Due to the simplicity and the ability to explain the spectroscopic and excited state properties, the MO theory in addition to easy adaptability for modern computers has gained tremendous popularity among chemists. The concept of directed valence, based on the principle of maximum overlap and valence shell electron pair repulsion theory (VSEPR), has successfully explained the molecular geometries and bonding in polyatomic molecules. 

The most useful approach in predicting the stereochemistry of coordination compounds is the Valence Shell Electron Pair Repulsion theory (VSEPR theory), which is based on the idea that the electron pairs around an atom will be arranged so as to minimize the repulsion between them. The qualitative foundations of this field were laid by Sidgwick and Powell1 in 1940 and by Gillespie... 

Valence shell electron pair repulsion theory (VSEPR)... 

Various have been developed and theories put forward to find an answer to the questions like why the molecules acquire a particular shape and what decides the bond lengths, bond angles and bond strength of the bonds that hold atoms in a molecule. One of these is Valence Shell Electron Pair Repulsion Theory (VSEPR Theory). 

Valence shell electron pair repulsion theory (VSEPR) provides a method for predicting the shape of molecules, based on the electron pair electrostatic repulsion. It was described by Sidgwick and Powell" in 1940 and further developed by Gillespie and Nyholm in 1957. In spite of this method s very simple approach, based on Lewis electron-dot structures, the VSEPR method predicts shapes that compare favorably with those determined experimentally. However, this approach at best provides approximate shapes for molecules, not a complete picture of bonding. The most common method of determining the actual stmctures is X-ray diffraction, although electron diffraction, neutron diffraction, and many types of spectroscopy are also used. In Chapter 5, we will provide some of the molecular orbital arguments for the shapes of simple molecules. 

As, and Sb, X is F, Q, Br, and I, and Y is O and S, are summarized in a review paper by Kuchitsu Trends observed in these molecules are well accounted for qualitatively by the valence-shell electron-pair repulsion theory (VSEPR) ... 

If we can draw Lewis structures for covalent molecules, we can predict their shapes by applying a few simple rules. The theory that accounts for the shapes of molecules is called valence shell electron pair repulsion theory (VSEPR theory) and is based on the reasoning that electron pairs attempt to get as far away from other electron pairs as possible because their negative charges repel each other. 

Valence shell electron pair repulsion theory (VSEPR) can be used to predict the shapes of molecules. According to this theory, the geometry of a molecule is such that the valence-electron pairs of the central atom are kept farthest apart to minimize the electron repulsions. Again, you have to view molecules in terms of Lewis structure so that the shape of the molecules can be predicted with the VSEPR theory. 

The shapes of many molecules and polyatomic ions can be predicted by using the valence-shell electron-pair repulsion theory (VSEPR). According to the VSEPR theory, electron pairs in the valence shell of the central atom of a molecule or ion repel one another and become arranged so as to maximize their separation distances. The resulting arrangement determines the molecular or ionic shape when one or all of the electron pairs involved form bonds between the central atom and other atoms. 

Valence-shell electron-pair repulsion theory (VSEPR) Explanation for the geometric arrangements and angles of unshared and shared electron pairs around the central atom by consideration of repulsions among electron pairs. 

We have seen earlier (Chapter 4) that the valence shell electron pair repulsion theory (VSEPR theory) can be very usefully applied to explain the shapes of simple covalent molecules and polyatomic ions built around a central atom. 

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