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Ease of Reduction
| We can also relate the ease of reduction of nonmetals to
position on the periodic table. Remember, reduction means gaining electrons. Let's use the
halogens (fluorine, chlorine, bromine and iodine) as examples. |
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| The most easily reduced of these is fluorine. It has the greatest tendency
to gain electrons. Next would be chlorine, followed by bromine and iodine. This is also
summarized in example 14 in your workbook. |
| Ease of reduction |
F
Cl
Br
I |
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| Remember that reduction and oxidation are related processes. They are the
opposites of one another. If you reduce fluorine, it become fluoride ion. If you reduce
chlorine, it becomes chloride ion; reducing bromine turns it into bromide ion and reducing
iodine turns it into iodide ion. These ions now have electrons which can be lost; that is,
the ions can be oxidized. The reactions can be reversed. |
| Reduction process |
F
 F-
Cl Cl-
Br Br-
I I- |
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| We can rate the ease of oxidation for these negative ions
by reversing the order of the ease of reduction of the atoms. So the most
easily oxidized of those four ions would be iodide. The next most easily oxidized would be
bromide; next, chloride; and the most difficult to oxidize would be fluoride ion. The difficulty
of removing an electron from a fluoride ion matches the ease of adding
an electron to a fluorine atom. An atom of fluorine has a very strong tendency to gain an
electron. Once it has the electron and becomes an ion, the ion will have a very weak
tendency to lose that electron. |
| Ease of oxidation |
I-
Br-
Cl-
F- |
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| We can add these ions to our ease of oxidation list by writing iodide,
bromide, chloride and fluoride ions below aluminum. (As is shown in example 15.) Notice
that I said the ions, not the elements. This is because this is an oxidation list and
those elements gain rather than lose electrons. As you can see, a lot can be figured out
from the periodic table. |
| Ease of oxidation |
K
Na, Ca
Mg
Al
I-
Br-
Cl-
F- |
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However, position on the periodic table is not the sole determiner of the ease of
oxidation. This is especially true when it comes to the transition elements. Also, these
reactions usually take place in solution and the tendency of water to bond to ions and
thus stabilize them, varies from ion to ion. So that comes into play, also. The method for
determining the actual order for ease of oxidation is experimental. We
take up that aspect on the next page.
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E-mail instructor:
Eden Francis
Clackamas Community College
©1998, 1999 Clackamas Community College, Hal Bender
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