Valence+Bond+Theory-+orbitals;+resonance;+sigma+and+pi+bonds

=Valence Bond Theory = ====The //Valence Bond Theory// explains the joining of atoms, each possessing their own orbitals and electrons, forming covalent bonds of a molecule. Under this theory, two atoms form bonds when a maximum of two electrons are shared in the overlapping orbitals.====

==== //Five basic electron-domain geometries:// Linear, Trigonal planar, Tetrahedral, Trigonal bipyramidal, Octahedral (predicted by the [|VSPER] model)====

**Shapes of each hybridization can be seen:**
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 sp hybridization : the s orbital (2s) and one of the p orbitals are mixed

 * ==== formation of two sp hybrid orbitals ====
 * ==== has a linear orientation ====


 * ====formation of three sp2 hybrid orbitals====
 * ====has a trigonal planar, one atom at the center and three atoms at the corner (looks like a triangle), orientation ====

sp3 hybridization: the s orbital and three p orbitals are mixed

 * ====formation of four sp3 orbitals ====
 * ====has a tetrahedral, one central atom with four atoms branching off, orientation====

sp3d hybridization: the s orbital, three p orbitals, and one d orbital are mixed

 * ====formation of five sp3d orbitals====
 * ====has a trigonal bipyramidal, one atom at the center and five atoms at the corners, orientation====

sp3d2 hybridization: the s orbital, three p orbitals, and two d orbitals are mixed

 * ====exception to the octet rule====
 * ====has a octahedral, a central atom with six atoms in each corner, arrangement====

=== ===

**See the hybridization in action!:**
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==== The way to truly represent t he structure would be to have an average of all structures. However, we can represent these various structures individually known as //resonance structures//. These structures are drawn and marked with an double sided arrow between each structure.====

Sigma (σ) & Pi (π) Bonds
====A //sigma bond// ( **σ** ) is a covalent bond between two nuclei in the overlapping region. In most cases, sigma bonds are also known as single bonds. It is important to keep in mind that between each pair of atoms there is exactly one sigma bond. //Pi bonds// (** π **) are similar to sigma bonds except that they describe multiple bonding. Pi bonds are covalent bonds where the overlapping regions are above and below the "internuclear axis"*====

In double bonds, there is one sigma bond and one pi bond.
In triple bonds, there is one sigma and two pi bonds.

[[image:double_bond.JPG align="left" caption="C=C is a double bond; one bond is a σ bond, and one is a π bond"]]
In a scenario involving a triple bond, one of the three bonds would be a sigma bond, and the other two would be pi bonds.

An overview of sigma and pi bonds can be seen here: media type="youtube" key="ree49ge4VA4" height="385" width="480"

//covalent bonding:// [|http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/covalent_bond/bond_class.jpg] //sp hybridization:// []
 * images:**

Moore, John; Richard H. Langley. (2007) //5 Steps to a 5 AP Chemistry, 2008-2009 Edition (5 Steps to a 5 on the Advanced Placement Examinations)//. New York: McGraw-Hill [|ISBN 978-0-07-148855-6]
 * References:**