Redox is
short form for "
reduction-
oxidation." A redox reaction refers to any reaction that involves the
transfer of
electrons from one
reactant to another, or a change in the degree
electrons are shared. Taking an
electron from a substance is called
oxidation, while adding an electron to a substance is called
reduction. The term
reduction may seem
counter-intuitive since you are adding an
electron, but it refers to a reduction in the charge of the
reactant. The reactant that gives up
electrons is called the reducing agent. The reactant that takes
electrons is called the oxidizing agent. If this seems mildly confusing, allow me to
illustrate with a very simple example.
+ -
Na + Cl --> Na + Cl
Note for those with
rusty chemistry:
sodium has one electron in its outer shell, and
chlorine requires one more electron to fill it's
valence shell.
Here,
sodium is
oxidized and
chlorine is
reduced. The end result is
table salt. In this example, an
electron is actually transfered. In my last example I will use a common redox reaction in which
electron sharing is altered. I give you
burning methane.
------------ Oxidation -------
V V
CH4 + 2 02 -> CO2 + Energy + 2H2O
^ ^
------------------- Reduction ------------
Since
oxygen is highly
electronegative, the shared
electrons in the
carbon dioxide product are shifted away from the
carbon. Since the
covalent electrons in
methane are evenly shared, the
methane has been oxidized. Along the same vein, the
covalent electrons are shared evenly in the
oxygen molecule, but are shifted away from the
hydrogen in the
water molecule. Thus the
oxygen molecule has been reduced.
Redox reactions often have oxygen as one of the reactants, such as
burning,
rusting and
metabolism.