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This
section is about covalent chemical bonds and covalent bond energies. We
can define these terms as the forces that cause a group of atoms to act as
a unit. To find the energy in a certain compound, we look at the models. A
model is an attempt to explain how the compound looks and acts, but is not
actually the real thing.
Remember
that a bond does not always equal a certain number. When working with bond
energies, you are working with the average of all the bond energies for
that bond. Also in bonding, we can have more than just a single electron
being shared to become a bond. if we have two electrons shared, we have a
double bond, and then with three electrons being shared, we have a triple
bond. The energy required to break a bond dramatically increases when more
electrons are shared.
In chemistry, you will hear about enthalpy for the rest
of your life. Enthalpy will be the over-all energy released or absorbed in
a reaction. To find enthalpy, we use this equation:
Enthalpy (H) = energy of bonds broken - energy of bonds formed.
(ex.) H2 + F2 ---->
2HF. Here we have one bond of H-H plus one bond of F-F. Both of these
bonds are broken and the remaining atoms form two H-F molecules. We look
up the bond energies for this reaction and use our equation:
Enthalpy = [1*(432) + 1*(154)] -
[ 2*(565)] = -544kJ
Multiplying the bond energy by the number of that type of bond formed is
extremely important.
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