8.2 Lewis Dot Structures
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Octet Rule
The octet rule states that most atoms will transfer electrons (ionic bonding) or share electrons (covalent bonding) to obtain a total of 8 electrons in its valence shell.
| OCTET RULE EXCEPTIONS |
|---|
| 1. A few atoms routinely go under the octet rule H only 2 Be only 4 B and Al only 6 |
| 2. Third row and lower can exceed the octet rule |
| 3. Molecules with odd numbers of electrons (ex. NO) |
How to Draw Lewis Structures
| 1. Set up skeleton with single bonds (central atom is the atom which can make the most bonds). |
| 2. Fill the octets of the outside atoms with lone pairs of electrons. |
| 3. Any remaining valence electrons go on central atom. |
| 4. Once all electrons are used, form multiple bonds to the central atom if not “full.” |
CH4 Lewis Structure
NH3 Lewis Structure
HCN Lewis Structure
Formal Charge
Formal Charge = Number of Valence e- – [Nonbonding e- + ½ bonding e-]
Formal Charge = Number of Valence e- – [“dots” + “lines”]
CO2 Lewis Structure
N2O Lewis Structure
SF4 Lewis Structure
NO3- Lewis Structure
