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Chemistry: Formation of Multiple Covalent Bonds

Formation of Multiple Covalent Bonds

The examples we just discussed explain why single covalent bonds are formed between two atoms. However, two atoms sometimes bond more than once. How does this work?

Let's use the example of O2. Both oxygen atoms have six valence electrons, meaning that they each need two more to be like neon. Fortunately, by combining both sets of unpaired electrons simultaneously, they both achieve their desired electron configurations:

By combining more than one unpaired electron at a time, a double bond is formed, and both oxygen atoms end up with eight valence electrons.

Figure 9.3By combining more than one unpaired electron at a time, a double bond is formed, and both oxygen atoms end up with eight valence electrons.

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It's common to assume that if an atom forms a triple bond in one compound, it will always form triple bonds in covalent compounds. Remember that each example is unique and requires separate analysis.

Because the two oxygen atoms are sharing four electrons at the same time, two covalent bonds are formed between them. We refer to these two covalent bonds as being a "double bond." In the same way that this double bond was formed, you can imagine triple bonds being formed if two atoms each have three unpaired electrons. An example is nitrogen (N2).

When two atoms that each have three unpaired electrons combine with each other, the result is a triple bond.

Figure 9.4When two atoms that each have three unpaired electrons combine with each other, the result is a triple bond.

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Excerpted from The Complete Idiot's Guide to Chemistry © 2003 by Ian Guch. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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