Themes > Science > Chemistry > Inorganic Chemistry > Chemical Bonding > Lewis Structures
Lewis Structures, named after G.N. Lewis, show how valence electrons are arranged. He determined that the stable molecule has the configuration of a noble gas. For this we count the number of electrons each atom has in its valence shell, and then we can count how many more valence electrons are needed to make it have the configuration of a noble gas, which would be eight valence electrons. Here are the basic rules to finding the more simple Lewis structures:
1. Count valence electrons on each atom
2. Use a pair to make a bond (A bond in between two atoms is going to be two electrons that are shared between those atoms)
3. Arrange remaining atoms to satisfy the electrons
ex. Finding the Lewis Structure for water, H2O:
1. H= 1 valence electron, O= 6, 2 H's + 1 O= 8 valence electron
2.The model must look like H:O:H (remember, the two dots represent a pair of electrons)
3.We only have four electrons in our model, and we added eight, so we assume that the other four are on the central atom, making our final model H:O:H
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As you can see, the two electrons that are unpaired are free to bond with the sole electron of the Hydrogen ion making H2O |
In time these begin to be very easy, but these are only the simple structures. In the next section, we will discuss the exceptions to the basic rules of Lewis Structures.
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