Valence Bond Theory
Bret Edwards
Models are important to have in any field because they help to explain and guide you in
further research and development of a theory or idea. One of the many models related to
chemistry is the valence bond theory model. Another example of a pandemic scientific model is
the atomic model; it increases the ability to understand atoms in general as well as how they
function.
According to an unknown author, valence bond theory is a way of describing the electron
pair bonds that occur in covalent compounds.” (Author unknown,
http://intro.chem.okstate.edu/1314f97/chapter9/wed123971.html) Two theories have evolved
from quantum mechanics that help the chemists in describing the experimental observations in
terms of the atomic or molecular orbitals in a compound. One is the valence bond theory the
other is the molecular orbital theory. This theory has two important ideas: an orbital on one atom
comes to occupy a portion of the same region of space as an orbital on the other. When this
occurs the two orbitals are said to overlap, and there can be no more than two electrons in the
orbitals and their spins must be opposite
Once a valence electron is inside an orbital, one atom overlaps with an orbital containing
a valance electron on another atom the electrons in the orbitals begin to move around both atoms.
The attractions from the electrons from both nuclei pull the atoms together. The strength of the
bond depends on the amount of overlap; the more the orbitals overlap, the stronger the bond.
Again remember the two overlapping orbitals must have opposite spins and cannot hold more
than two electrons.
Chemical bonds can occur when the nuclei or the electrons of two atoms are attracted to
each other through electromagnetic force between the charges of the opposites. Basically, they
are three-dimensional atoms, with the nuclei connected to each other, bonded together in a
straight line. When there is a pair of electrons by themselves, it influences the shape of the
molecular geometry of the bond. The molecular geometry shape can be found using the VSEPR
(valence shell electron pair repulsion) theory. The VSEPR theory contrasts with the valence bond
theory because valence bond theory determines the molecular shape through the orbitals that are
firmly unrestricted for bonding.
The valence bond is considered as a weakly coupled bond because it has small overlaps.
As the overlap of the orbitals increase, the strength of the bond increases as well.
There are many different ways of understanding how atoms bond with each other.
Because there is not a scientific law that explains the bonding in precise and accurate way,
depending on the situations given, each method has its own advantages and disadvantages. The
two basic theories in chemistry are valence bond theory and the molecular orbital theory. The
valence bond theory and the molecular orbital theory are complementary to each other because
some parts of the valence bond theory is beneficial such as providing a very accurate description
for chemical reactions, while the molecular orbital theory could be beneficial in explaining the
bonding in another area.
Sources

http://intro.chem.okstate.edu/1314f97/chapter9/wed123971.html

http://web.viu.ca/krogh/chem122/VALENCE%20BOND%20THEORY.pdf

http://www.chemistryexplained.com/Te-Va/Valence-Bond-Theory.html