Carbon

The focal or central element of organic and biochemistry is carbon. Let's start with a review of the atomic properties of carbon.

If I were to give you a periodic table and ask you to tell me something about carbon, you should be able to tell me things like this:

Periodic Table showing position of carbon.[61pt1.JPG (15208 bytes)]

"Carbon is element number 6, which means that it has six protons in its nucleus and a total of six electrons. Two of those electrons are in the first shell and the remaining four electrons are valence electrons which are found in the outermost shell of carbon. Carbon is a nonmetal, but it is not very electronegative, because it is not very far to the right side of the periodic table. Because it is a nonmetal, it likes to gain electrons in order to complete its outer shell. Because it is not very electronegative, it does not have the ability, in most cases, of completely gaining electrons to form negative ions. Consequently, it forms covalent bonds in which it shares its electrons with other elements. It can also bond to other atoms of carbon to form covalent bonds from one carbon to another. It is bonds of this type that give carbon its very central role in life."

You may or may not think so, but you knew all that, except perhaps the last comment. If you do not believe me, just sit back for a minute and think about the comments above and they all should sound familiar. If you go back through your memory or your notes and take the time to think about each of these statements, I am pretty sure that you will find that you have been able to make those statements at one time or another during this course.

One reason for this digression is to let you know that you have learned quite a bit of chemistry and that you should pat yourself on the back at this time for having learned it.

Another reason is that you may well have forgotten a lot of that material that you learned, and I wanted to bring it back into your mind before we start to use that information.

The properties of carbon listed above combine to give it a seemingly unique ability to form a virtually infinite number of stable compounds which feature chains of carbon atoms hooked together in a variety of ways. Its small size, intermediate electronegativity, and four valence electrons allow for quite a variety of bond types (single, double or triple as well as polar or nonpolar) and orientations (tetrahedral, trigonal planar or linear). When this is combined with the ability to form different carbon-atom chain combinations, it provides us with more molecules and molecular shapes than words can describe.

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E-mail instructor: Eden Francis

Clackamas Community College
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