1. Lewis Dot Diagrams

2. Review How many valence electrons do most atoms want?8
Who is the exception to this rule?
Hydrogen & Helium

3. Review In a chemical bond, do alkali metals gain or lose electrons?
In chemical bonds do metals form cations or anions?
Cations
In chemical bonds, do non-metals form cations or anions?
Anions

4. Only show valence electrons
One “dot” = one electron

5. Hydrogen
Beryllium
Boron H Be B
Carbon
Nitrogen
Oxygen C N O

6. Illustrating Compounds
Two types of compounds:
Ionic
Covalent
Ionic = a metal bonded with a nonmetal
Covalent = two nonmetals

7. Ionic Lewis Dot Diagrams
In ionic bonds electrons are transferred
Example: Sodium Chloride Na Cl Cl Na

8. Mg O Mg O Practice Illustrate a Lewis Dot Diagram for Magnesium Oxide: O

9. Covalent Lewis Dot Diagrams
In covalent bonds electrons are shared.
Lines are used to represent shared electrons
One line means each atom is sharing one electron with the other
(1 line = 2 electrons)

10. In an H2 molecule, each hydrogen shares its one electron with the other hydrogen.
We illustrate this sharing with a line: H H

11. Illustrate a bond between two chlorine atoms:Cl Cl

12. Sometimes atoms need more than one electron to complete their outer shells.
We call this a double bond and illustrate using two lines: O O

13. Illustrate a bond between two Sulfur atoms:

14. Occasionally an atom will need to triple bond to fill its valence shell.
To illustrate triple bonds we use three lines: N N

15. Illustrate a bond between two phosphorus atoms:

16. Many compounds consist of more than two atoms
How would we illustrate a Lewis Dot Diagram for a Phosphorus atom bonded to 3 chlorines?

17. The atom that needs the most electrons always goes in the middle!

18. How would we illustrate a Lewis Dot Diagram for a Hydrogen bonded to a Carbon and Nitrogen?